Allow user to create and delete tables and databases through pseudo-tables. Add primary_key field to rethinkdb.table_config.
Add tests for creating/deleting tables and databases by creating/deleting pseudo-table rows. Also, fix tests that broke when pseudo-tables started returning cursors rather than arrays.
Factor out check for DB/table existence into a helper function
Merge branch 'tim_config_insert_delete' into reql_admin