LP1183553 - Default filter option for configuration screens

In the staff client, the AutoGrid widget is used to render configuration
lists, and by default, the setting 'showLoadFilter' is turned off.  It
seems more useful to turn it on by default so that any configuration
screen can use it unless its template sets it off.

Signed-off-by: Steven Chan <schan@sitka.bclibraries.ca>
Signed-off-by: Pasi Kallinen <pasi.kallinen@pttk.fi>
Signed-off-by: Ben Shum <bshum@biblio.org>
LP1183553 (continued) - Fix applied filters

The filter dialog kept the previous filter around and then joined the
new one with it. This repairs that issue and applies the new filter
options on subsequent loading.

Signed-off-by: Pasi Kallinen <pasi.kallinen@pttk.fi>
Signed-off-by: Ben Shum <bshum@biblio.org>