Role-based result row limit in Query Editor

Admin users should be able to define the result size limit for other users. By default, only admin users can have the 'No Limit' option.

When a user enters a limit in the Query Editor that exceeds the restricted limit set by the admin, an error should be shown and the change should be rejected.

I note that the *No Limit *option is enabled on the bottom results page, but it is not added to the query tab, therefore please remove it from the bottom as well. Otherwise, the maxscale server would go out of memory if user selects millions of data.