Users sync frontend

 * Implemented functions called by framework when users are created or edited
 * Added a checkbox to enable Samba4 to a user
 * When a user is modified, samba4 backed is notified
 * A user can have its samba status as disabled or enabled
 * When enabling Samba4 to a user that existed before Samba4 was provisioned
   He is asked to submit a new password
 * When a user changes his password, the newer one is passed to Samba4
Merge branch 'samba4-poc' of github.com:Zentyal/mmc into samba4-poc

Conflicts:
	mds/web/modules/samba4/Makefile.am