More 2.3 Fixes

- Adds necessary classes for the search/clear filter field to fit into the new UI
- Adds primary-button classes where applicable
- Fixes the import window (removed height needs check in 2.2.x for undesirable behavior)
- Fixes the remove tag/cross button on the special tag field (see https://github.com/modxcms/revolution/issues/11630#issuecomment-51174331)