Sent zentyal-usercorner trigger on install / upgrade to restart it if it's installed
Fixed external mail retrieval configuration form from user corner. Restart usercorner on installation / upgrade time so the new code is available there too
Merge branch '3.4' into cperello/user-corner-mail-fixes

Conflicts:
	main/mail/ChangeLog
	main/users/ChangeLog
Merge pull request #1247 from Zentyal/cperello/user-corner-mail-fixes

Cperello/user corner mail fixes