Add button to remove saved search query

TODO: move all saved query related logic into its own manager instead of
leaving them in SearchFragment.

Change-Id: I9635140eb507331246f9035a23138421cfa4b50a
Fix: 27391895
Test: make RunSettingsRoboTests

tests/robotests/src/com/android/settings/search2/SearchFragmentTest.java

@@ -276,7 +276,6 @@ public class SearchFragmentTest {
 
     @Test
     public void onLoadFinished_ShowsFeedback() {
-
         when(mFeatureFactory.searchFeatureProvider
                 .getDatabaseSearchLoader(any(Context.class), anyString()))
                 .thenReturn(new MockDBLoader(RuntimeEnvironment.application));