Remove workgroup from gui and move netbios name to advanced section

- workgroup does not need to be specified since we query for it
- netbios name often doesn't need to be changed, unless you're doing
  weird thing, in which case you know what you're doing

Ticket: #5286
Ticket: #5285
Rework AD code to understand m0ar thingz
Nuked __init__ in previous commit, bring it back!
Readability fixes
"proper" fix for user/group name resolving.

Ticket: #5310
Don't cache.
Sane file and directory default permissions

Ticket: #5314
Merge branch 'adremix'