Add p5 (processing python) Image I/O support

[myselfhimself]

Processing has 2 Python implementations:

• processing.py, a Jython binding of the Processing Java library, with a Python 2.7 syntax - will be difficult to link with the C / shared library world
• p5 (or p5py) is in pure-Python >3 with a slightly differing API and using PIL in Python

Both libraries are used by multimedia students and professionals, in an even simpler way as Pygame does, for (non-)interactive animations or games. A multimedia teacher in Germany, held a talk about it during this years's Libre Graphics Meeting: Processing Python Mode for Creative Coding and Teaching

We could discard implementing a bridge for processing.py and focus on image I/O with the p5 Image class. Possibly with its Pixels() context manager or just the load() image method.