CMake: install missing module

- The CMake modules for Calamares expect to find CMakeColors
 - Also the translation support macro
 - Restore CalamaresUse.cmake
   - File was removed after 3.1 in db105079, but it is actually useful
     for out-of-tree modules. Restore it and massage into better shape.
   - Simplify by adding path to the search path (otherwise the individual
     macro files would also have to switch to including with a full path).

CMakeLists.txt

@@ -340,16 +340,20 @@ file( RELATIVE_PATH CONF_REL_INCLUDE_DIR "${CMAKE_INSTALL_FULL_CMAKEDIR}" "${CMA
 
 configure_file( CalamaresConfig.cmake.in "${PROJECT_BINARY_DIR}/CalamaresConfig.cmake" @ONLY )
 configure_file( CalamaresConfigVersion.cmake.in "${PROJECT_BINARY_DIR}/CalamaresConfigVersion.cmake" @ONLY )
+configure_file( CalamaresUse.cmake.in "${PROJECT_BINARY_DIR}/CalamaresUse.cmake" @ONLY )
 
 # Install the cmake files
 install(
     FILES
         "${PROJECT_BINARY_DIR}/CalamaresConfig.cmake"
         "${PROJECT_BINARY_DIR}/CalamaresConfigVersion.cmake"
+        "${PROJECT_BINARY_DIR}/CalamaresUse.cmake"
         "CMakeModules/CalamaresAddPlugin.cmake"
         "CMakeModules/CalamaresAddModuleSubdirectory.cmake"
         "CMakeModules/CalamaresAddLibrary.cmake"
         "CMakeModules/CalamaresAddBrandingSubdirectory.cmake"
+        "CMakeModules/CalamaresAddTranslations.cmake"
+        "CMakeModules/CMakeColors.cmake"
     DESTINATION
         "${CMAKE_INSTALL_CMAKEDIR}"
 )

CalamaresUse.cmake.in

@@ -0,0 +1,29 @@
+# A setup-cmake-things-for-Calamares module.
+#
+# This module handles looking for dependencies and including
+# all of the Calamares macro modules, so that you can focus
+# on just using the macros to build Calamares modules.
+# Typical use looks like this:
+#
+# ```
+# find_package( Calamares REQUIRED )
+# include( "${CALAMARES_CMAKE_DIR}/CalamaresUse.cmake" )
+# ```
+#
+# The first CMake command finds Calamares (which will contain
+# this file), then adds the found location to the search path,
+# and then includes this file. After that, you can use
+# Calamares module and plugin macros.
+
+if( NOT CALAMARES_CMAKE_DIR )
+    message( FATAL_ERROR "Use find_package(Calamares) first." )
+endif()
+set( CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${CALAMARES_CMAKE_DIR} )
+
+find_package( Qt5 @QT_VERSION@ CONFIG REQUIRED Core Widgets )
+
+include( CalamaresAddLibrary )
+include( CalamaresAddModuleSubdirectory )
+include( CalamaresAddPlugin )
+include( CalamaresAddBrandingSubdirectory )
+