SMBFS registry shares instead of user shares.

The commits 40222af and 0f6d601 is already in pull #1412, but this pull is dependent on that, so that would have to be accepted first.


A registry share is much more configurable than a user share, that basically only accepts path, comment and guest_ok. A registry share supports every option that one would have in smb.conf(5).


The only change, for the user/admin, is that the 'acl' option is no more. Instead there is the 'writeable' boolean.