VCard 4 support detection; new ez-vcard version

* detect CardDAV VCard version support using supported-address-data + test
* account setting for supported VCard version
* don't ask for calendar details when querying CardDAV collections
* don't ask for address book details when querying CalDAV collections
* ez-vcard update to 0.9.5 (fixes #268), adapted exception handling
* refactoring: unnecessary DavProp prefixes removed
Don't require capabilities on home sets that MAY not be available on these collections (fixes #289)
Merge upstream
Fix deleting tasks