Add summary to notification filtering

Change-Id: Ie02165f72e67b2fc6aa086de61303a53a7ee4470
Disable settings search on all subactivities.

This leaves the search in place in multi-pane configurations, and keeps
it only in the main settings screen for single-pane configurations.

Change-Id: I2db74193d534b66e1faf20293996c611621dfe58