On the way to use database profiles

core of the change result in the options:

--ADUC: simulate ADUC, i.e. have no objectClass, but msRFU30* and other fields
--rfc2307: be POSIXly correct, i.e. have objectClass and no fields off the scheme
--hybrid: similar to ADUC, but with objectClass added
Allow schema to be passed in ENV SAMBA_POSIX_SCHEMA
Removed unused code
Added unposix command to user and group

* removed group set --unposix, which served a similar purpose
Made group set adhere schema settings
Added group fix command
Fixed group fix
Added user fix command
Get Domain SID from domain entry
Added group membership fixing for user fix
Learned something about how AD manages memberships and primaryGroupID

* put pointers into the code marking what to do
Added group getent --include-primary-group
Cared for primaryGroupID membership in group add and group remove