CMake: add license headers, copyright

Since we install the CMake files now, also put license headers in them.
These files are intended to help plugin and branding component authors
write them in a simple Calamares-idiomatic way.

CMakeModules/CalamaresAddBrandingSubdirectory.cmake

@@ -1,3 +1,23 @@
+# === This file is part of Calamares - <https://github.com/calamares> ===
+#
+#   Calamares is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Calamares is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+#
+#   SPDX-License-Identifier: GPL-3.0+
+#   License-Filename: LICENSE
+#
+###
+#
 # Support macros for creating Calamares branding components.
 #
 # Calamares branding components have two parts:

CMakeModules/CalamaresAddLibrary.cmake

@@ -1,3 +1,25 @@
+# === This file is part of Calamares - <https://github.com/calamares> ===
+#
+#   Calamares is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Calamares is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+#
+#   SPDX-License-Identifier: GPL-3.0+
+#   License-Filename: LICENSE
+#
+###
+#
+# Support functions for building plugins.
+
 include( CMakeParseArguments )
 
 function(calamares_add_library)
@@ -64,7 +86,7 @@ function(calamares_add_library)
     endif()
 
     # add link targets
-    target_link_libraries(${target} 
+    target_link_libraries(${target}
         LINK_PUBLIC ${CALAMARES_LIBRARIES}
         Qt5::Core
         Qt5::Gui

CMakeModules/CalamaresAddModuleSubdirectory.cmake

@@ -1,3 +1,26 @@
+# === This file is part of Calamares - <https://github.com/calamares> ===
+#
+#   Calamares is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Calamares is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+#
+#   SPDX-License-Identifier: GPL-3.0+
+#   License-Filename: LICENSE
+#
+###
+#
+# Function and support code for adding a Calamares module (either a Qt / C++ plugin,
+# or a Python module, or whatever) to the build.
+#
 include( CalamaresAddTranslations )
 
 set( MODULE_DATA_DESTINATION share/calamares/modules )

CMakeModules/CalamaresAddPlugin.cmake

@@ -1,3 +1,23 @@
+# === This file is part of Calamares - <https://github.com/calamares> ===
+#
+#   Calamares is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Calamares is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+#
+#   SPDX-License-Identifier: GPL-3.0+
+#   License-Filename: LICENSE
+#
+###
+#
 # Convenience function for creating a C++ (qtplugin) module for Calamares.
 # This function provides cmake-time feedback about the plugin, adds
 # targets for compilation and boilerplate information, and creates

CMakeModules/CalamaresAddTranslations.cmake

@@ -1,3 +1,25 @@
+# === This file is part of Calamares - <https://github.com/calamares> ===
+#
+#   Calamares is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Calamares is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+#
+#   SPDX-License-Identifier: GPL-3.0+
+#   License-Filename: LICENSE
+#
+###
+#
+# This file has not yet been documented for use outside of Calamares itself.
+
 include( CMakeParseArguments )
 
 # Internal macro for adding the C++ / Qt translations to the