[buteo-sync-plugin-caldav] Use a time range for quick syncs

Some servers (e.g Memotoo) don't emit a proper reply if we try to
fetch the etags with a defined time range. This commit is a partial
revert of 782ef9db20125f36fec4bbf78ac04a0d335debc7.
Now the client will only store events 6 months older than current date
and 12 months in the future.

Conflicts:
	src/notebooksyncagent.cpp
[buteo-sync-plugin-caldav] Fix QUrl creating from percent encoded strings

Calendar urls are currently saved in percent encoded format
when passed them in this format to QUrl::setPath a recoding
can happen(Tolerant mode is the default) breaking the original
server path, so we decode them first.
Bump version
update
[buteo-sync-plugin-caldav] Raise CredentialsNeedUpdate flag after unauthorized access
Bump version
Fix ICal data encoding to match the Content-Type header

Some CalDAV servers (SOGo at least) seem a bit picky
about the data encoding and if the ICal data encoding
does not match the one specified in the Content-Type
HTTP header then the creation or update is rejected.
Bug is exhibited when any ICal property contains
non-ASCII characters.

Testing was performed with the latest SOGo stable
release.
update