Implement godot-annotation-processor

[chippmann]

Implement a annotation processor like here: https://github.com/utopia-rise/godot-kotlin/tree/master/tools/godot-annotation-processor

The annotation processor should listen to the annotation's defined here: #68 , #70 , #69.

It should gather the descriptor classes in these lists:

• classDescriptors
• propertyDescriptors
• propertyDescriptors (for signal annotations)
• funcDescriptors

It should gather those informations using the mpApt project: https://github.com/Foso/MpApt
But should NOT pass any MpApt specific informations to the godot-entry-generator so it does not need any dependency to MpApt!