Move Quidem tests from JdbcTest into their own class

Quidem tests are currently in JdbcTest (testRunAgg etc.). You have to remember to add a test method testRunFoo if you add sql/foo.iq.

Move them into their own test QuidemTest. Adding a new .iq file must be sufficient to make the test run with the rest of the suite. But you should be able to add a method testSqlFoo (note how the name is derived from the path "sql/foo.iq") and override how the Quidem test is invoked.