* start some resource fiddling
* start some resource fiddling
* initiate a real resource manager
* fix color flicker in rendering
* delete unintended constructors
and add a convenience function to reset the render-image (from the
original image, aka. clone again)
* [OpenGL deprecation warning]
The compiler said that these functions are "deprecated". They seem to
be useless anyway...
* various improvements
* add resource enumerator and documentation
* fix constness stuff
* use existing iterator for insertion
* init unit tests
* rm bogus file
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Co-authored-by: m-aXimilian <keuffnermax@gmail.com>