Utilize the paths for a library in a project to look for paths to use for QML_IMPORT_PATH to save having to add them explicitly

Utilize the paths for a library in a project to look for paths to use for QML_IMPORT_PATH to save having to add them explicitly. This can be done for qmake and CMake projects then, it would still be possible to set it manually, but it could look at the known library paths for added libraries and include those as well automatically.