Filter panel should not update filter until all changes are made.

Right now, every change of option to the filters panel causes a server request to re-filter, and if I want to change 5 things, that is at least 4 extra server requests that will be discarded. This seems to slow down the final filter request until the previous server requests finish.

I would prefer to update all the filter selections, then click a "Update Filter" button to cause the single server request. I think this would improve usability and greatly reduce load on the server.