extend PreferenceActivity for title text on a single pane mode

startPreferencePanel() ignores titleText on a single pane mode
this commits extends PreferenceActivity by adding EXTRA_SHOW_FRAGMENT_TITLE_TEXT to intent

ported from CM9, http://review.cyanogenmod.org/#/c/14919
AOSP part verified, but not merged

Change-Id: Ie0702dc20b17504148f4da9cc83a6d7865d95423