#25 Query Service: Limit Capabliity DB-Specific

[Dave Depinet]

Currently, the "Limit" capability in the query service
works only with mySQL. This could be improved by
either:
1) Just use the limit to set the maxRows on the
statement. That may not prevent all the database
work, but it won't retrieve any more rows than are
needed. And this is vendor-independent.
2) Add some capability to get a database-dependent
limit string in the RDBMS plugin and use that capability in
the query service.

Option 1 is preferred. If the user must specify some
DBMS-specific stuff in their query, they still can-- it just
won't be portable to another DBMS.