Automatize part of the initPlugin.cpp file generation

[bakpaul]

Methods used by the plugin manager such as :

• initExternalModule()
• getModuleName()
• getModuleVersion()
• getModuleComponentList()

Are usually exactly the same and only depends on information from CMake. The problem is that if mistake are introduced here, plugins might not be loadable anymore. It might be good to automatize the generation of such method.