davmail: 4.7.0 -> 4.7.1

Bugfix release, mainly for Carddav regression over EWS, also includes an NTLM support enhancement.

Enhancement:
- Improve NTLM support try to send hostname as workstation name instead of UNKNOWN
- Fix notification dialog message
- Prepare ExchangeSessionFactory refactoring
- Fix typo in french translation
- Fix broken Sourceforge link in About dialog

Carddav:
- Carddav: fix regression on contact update with empty field triggering DeleteItemField

(cherry picked from commit cf327c3dcfd442cea4368d76c59f72dcd5da6768)

[Bjørn: Cherry-picked from release-15.09 to master. (I guess merging
first to release-15.09 was a mistake.)]