VolumeZen: Sound & Notifications settings.

- Add sound settings under the newly combined Sound & Notifications
  top-level settings page.
- New slider preferences for setting audio stream volumes.
- Migrate checkbox prefs to switch prefs.
- New settings subpage for touch sounds.
- New settings subpage for "Showing notifications"
- New setting pref for displaying intercepted notifications in zen mode.
- New tri-state lockscreen notifications pref.
- Add priority + sensitivity options to app notification dialog.
- Remove badges on app notifications row, migrate to subtitle text.
- Migrate strings to common spot in strings.xml
- Remove heads up setting.
- Remove tweaks category (unused).
- Clean up notification settings, separate out into a code section per option.
- Clean up _settings.xml files, prefix each pref with option name.
- Add appropriate indexing data to each settings page.

Depends on f/b change Ic30aa575ae07650cee62c8c1d83b6bc69395cf0d

Change-Id: If700385a7d0057f6c4c4bcf6e648dcf88b8ebff2

src/com/android/settings/Settings.java

@@ -88,6 +88,9 @@ public class Settings extends SettingsActivity {
     public static class PrintJobSettingsActivity extends SettingsActivity { /* empty */ }
     public static class ZenModeSettingsActivity extends SettingsActivity { /* empty */ }
     public static class NotificationSettingsActivity extends SettingsActivity { /* empty */ }
+    public static class NotificationDisplaySettingsActivity extends SettingsActivity { /* empty */ }
+    public static class AppNotificationSettingsActivity extends SettingsActivity { /* empty */ }
+    public static class TouchSoundSettingsActivity extends SettingsActivity { /* empty */ }
 
     public static class TopLevelSettings extends SettingsActivity { /* empty */ }
 }