Clarify Handling of Matchgrid Renaming

It's not clear what the behavior should be for renaming a Matchgrid... should it immediately rename the actual table, or require the admin to do something (in which case how do we "remember" the old name)? Or maybe renaming shouldn't be permitted?

Also, Matchgrid specific API Users will need to be renamed, unless Match migrates to the Registry style of using the tenant ID as the username prefix.