Improve Preference highlighting

- use PreferenceFragment.onBindPreferences() to launch  highlighting
- improve SettingsPreferenceFragment code for highlighting: now we can
find the View to highlight thru its Tag if there is no ListAdapter available
- add HighlightingFragment for highlighting a View from its tag/key. This
is dealing with cases when the content is custom and not relying on
SettingsPreferenceFragment (like DataUsageSummary)

Also:

- improve DataUsageSummary so that onResume() is not recreating the
Tabs all the time
- add missing "android:keys" on some Security Settings preference files

Change-Id: Ib1dd8238fe2fb57c151d584c0810a0e0a5ad97c4