QuickSearchBox: Fix NPE if Google Apps not installed

Fixes:
Issue 6501: "Search" application stops when entering its settings
Issue 6502: "Search" widget doesn't work (no gapps installed)

Change-Id: I4855b80cc3b44ab7af488fc33e71da4a667512d5
Merge branch 'jb-mr1-release' of https://android.googlesource.com/platform/packages/apps/QuickSearchBox into HEAD

Change-Id: I035010efdd2d5ea65bdc005138da49e775fb4e5a
Issue 6501: "Search" application stops when entering its settings

QuickSearchBox is missing declared class com.android.quicksearchbox.preferences.SearchableItemsActivity
since ics and jb.
This changes add this class, use the existings headers, and redirect to SearchableItemsFragment when
user click in the settings icon of the search bar.

Patchset 2: Fixed comment header

Cherry-Pick: http://review.cyanogenmod.org/#/c/26421/2

Change-Id: Icd616492c1fa4dd6342e4983865530c7b9e1a037
Merge remote-tracking branch 'vanir/jb42' into CM