Add public dependencies to Config.cmake

To add public dependencies to the generated config, use e.g.

list(APPEND ${PROJECT_NAME}_PUBLIC_DEPENDENCIES "Boost COMPONENTS system thread chrono")

cmake/PROJECT_NAMEConfig.cmake.in.in

@@ -34,6 +34,8 @@ FIND_LIBRARY(@PROJECT_NAME@_LIBRARY @PROJECT_NAME@
   NO_DEFAULT_PATH
 )
 
+@@PROJECT_NAME@_PUBLIC_DEPENDENCIES_L@
+
 # Since this file is already part of the installation to be found, the configuration can be hard-coded at
 # installation time
 set(@PROJECT_NAME@_VERSION "@@PROJECT_NAME@_SOVERSION@")

cmake/create_cmake_config_files.cmake

@@ -53,6 +53,11 @@ foreach(LIBRARY ${LIST})
   endif()
 endforeach()
 
+set(${PROJECT_NAME}_PUBLIC_DEPENDENCIES_L "")
+foreach(DEPENDENCY ${${PROJECT_NAME}_PUBLIC_DEPENDENCIES})
+    string(APPEND ${PROJECT_NAME}_PUBLIC_DEPENDENCIES_L "find_package(${DEPENDENCY} REQUIRED)\n")
+endforeach()
+
 # we have nested @-statements, so we have to parse twice:
 
 # create the cmake find_package configuration file