Add PostLoader to Nalu

[FrankHossfeld]

Nalu offers a loader for the main application and loaders for each modules.

The loader of the main application will be executed first. After that, each module gets loaded and the module loader gets executed. The module loader might set up values and instances inside a module.

Nalu misses the possibility to do something after every module is loaded.

Add a new attribute inside the @Application annotation:

• postLoader

This attribute is optional.

If exists, execute it before the application continue to start.