PoC ili2py R&D Backend - Don't merge!

[signedav]

• Return URL in ilicache
• Integration of ili2c
• Simple ilifile downloader in pythonizer (might maybe be somewere else though) and see *
• Pythonizer Light from PoC ili2py R&D - Don't merge!  #153
• Settings Prophet - additional thingy with multigeometry
• Settings Prophet - enum detection
• fix arg problem in compiler todo care about param (it should not be considered)
• solve situation with requirments and relativ import paths...

* Not sure what model file download should be offered. On model adding by Model Baker Plugin it makes sense, that it gathers the URL as well and downloads it. But on e.g. XTF parse, it does not have the model URL, so maybe the function https://github.com/opengisch/QgisModelBakerLibrary/pull/153/files#diff-d2fdd9a0f0e6c13e663c41598dac607c5571830ead68fec357814e006fab4714R100 with all it's attributes (new IliModelFileCache) would make sense. It just seems not performant. This whole cache stuff is a little bit a mess.