CMake: improve documentation in the Config file

CalamaresConfig.cmake.in

@@ -1,8 +1,16 @@
-# - Config file for the Calamares package
+# Config file for the Calamares package
+#
 # It defines the following variables
 #  CALAMARES_INCLUDE_DIRS - include directories for Calamares
 #  CALAMARES_LIBRARIES    - libraries to link against
-#  CALAMARES_EXECUTABLE   - the bar executable
+#  CALAMARES_USE_FILE     - name of a convenience include
+#  CALAMARES_APPLICATION_NAME - human-readable application name
+#
+# Typical use is:
+#
+#    find_package(Calamares REQUIRED)
+#    include("${CALAMARES_USE_FILE}")
+#
 
 # Compute paths
 get_filename_component(CALAMARES_CMAKE_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
@@ -18,4 +26,7 @@ include("${CALAMARES_CMAKE_DIR}/CalamaresLibraryDepends.cmake")
 
 # These are IMPORTED targets created by CalamaresLibraryDepends.cmake
 set(CALAMARES_LIBRARIES calamares)
+
+# Convenience variables
 set(CALAMARES_USE_FILE "${CALAMARES_CMAKE_DIR}/CalamaresUse.cmake")
+set(CALAMARES_APPLICATION_NAME  "Calamares")