Merge branch 'dev' of https://gitlab.cvh-server.de/sboettger/foto-puzzler into SBO

doc/diagrams/class_diagram.uxf

doc/diagrams/class_diagram_short_version.uxf

src/general/MatchingCounterpiece.py

src/general/Puzzle.py

src/general/PuzzlePiece.py

src/general/PuzzleSolver.py

src/general/Side.py

src/image_processing/PuzzleConnector.py

src/image_processing/PuzzlePieceExtractor.py

src/image_processing/code.txt

src/puzzle solving/test_solving.py

test data/side.py

test data/test-puzzle.py