Naming of system groups

[Gervase Markham]

Maxwell Kanat-Alexander wrote:
> 	Indeed. I would probably suggest that any groups that existed in 2.16
> should have the same names as they did, and only groups added to 2.18
> should have the underscore added.

The problem with that is that we get inconsistencies going forward.

How about we rename them all, but continue to accept the legacy names of 
current ones in UserInGroup(), using a simple mapping table?

Lastly, the problem with the names currently is that they are exposed in 
the UI - which makes me less keen on the _ prefix, because it's ugly and 
not immediately human-understandable. Could we not prefix with bugzilla_ 
or system_ instead?

Gerv