Poor integration with Ldappc: subordinate-stem-query generates full table scans

A <subordinate-stem-query> does a "GroupNameFilter" with a scope of the specified stem and using "%" as the search value. That in turns
calls an API method which does a LIKE "%TERM%" query against the "grouper_attributes" table looking for "name", "displayName",
"extension" or "displayExtension" attributes with that value. So, yes, it certainly looks like a full table scan.

We don't currently provide an easy or efficient way in the API to find all child groups or stems. We could (and probably) should add that to
the API. After that we could either modify Ldappc to make use of those new methods or, perhaps, make the API smarter and have it use
the more efficient version if someone is doing a wildcard search.