Cf tests ci

Major change: This adds a test stage to the ci pipeline. Please note that this test will fail since one of the tests fails (see #1 (closed))

Other changes:

• job for building wheel (tests will run on wheel and not on local files)
• moved building of docs to pages job to speed up build stage
• added rules to only upload to PyPi if setup.py changed (i.e. version was incremented)
• added pip package caching to pipeline
• added exiftool as tests depend on it
• added expiration rules to artifacts