Highlights:
- Fixups on the async support. Perhaps the "sans-io" design concept wasn't such a great idea - quite some gaps in the async support has been identified and fixed,.
- Multi-server
get_calendars(): a singleget_calendars()call can now span multiple config-file sections (including glob/wildcard expansion), aggregating calendars from multiple servers into oneCalendarCollection. This was the idea (and has been implemented in myplannproject for quite some time), but fell short of getting into the v3.0-release. - Full async tutorial added to the documentation.