domain.py: Add a schemaupgrade option to apply missing 2008R2 schema

domain.py: Add a schemaupgrade option to apply missing 2008R2 schema

We've identified some cases where we've gotten our implementation of the
2008R2 schema wrong. We can fix these up for new provisions going
forward, but it'd be nice to have some way of fixing up the schema on
existing DCs.

A lot of what we're missing is already documented in Microsoft's
Sch45.ldf file:
https://technet.microsoft.com/en-us/library/dd378890(v=ws.10).aspx

Unfortunately we can't just apply the Sch45.ldf file using the existing
'samba-tool domain schema-upgrade' option because:
- We have got some of the Sch45.ldf changes, just not all of them.
- We already say the Samba schema objectVersion is 47 (2008R2), so
  there's no way to tell if the Samba instance does or doesn't have the
  missing changes (apart from querying each change).

We may want to add this to dbcheck eventually, but the simplest
implementation option for now is to extend the new schemaupgrade command
to allow us to specify a particular .LDF file to apply.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>