community/calcurse: Split out calcurse-caldav and fix deps

Merged Marian Buschsieweke requested to merge maribu/aports:community/calcurse into master

calcurse-caldav is a python3 script and therefore depends on python3 as well as on py3-httyplib2. It has additional dependencies on python modules outside of the standard libs, but those are optional and needed for OAuth support only.

Merge request reports