Introduced black formatting

Adds to changes in #514

removed syntax error in inca/processing/core/dependency_utils.py (is this even used?)
removed legacy folder (don't let the past haunt you! You can always find it in the git history)
formatted everything using black

FYI:

pip install black
black ./

Result:

note: the leftover six have since been fixed and added

These changes are opinionated. Feel free to reject this PR if you are uncomfortable with great but uncompromising formatting. (with great formatting, comes great ...)