SystemUI: Forward port Statusbar Clock and Date actions

Port of http://review.cyanogenmod.org/#/c/27795/4

PS2: Cleanup and address comments
PS3: Remove unused variables
PS4: Remove unused imports
PS5: Declare AP_PM_STYLE final
PS6: Add in @drawable/ic_notify_button_bg to header
PS7: Fix DateView layout. Clear activity stack

Begin old commit message-----------

Patch set 1-2: Initial port
Patch set 3  : Fixes date click action
Patch set 4  : Remove unused import

Includes:
- Add onClick action to notification clock and date
  In expanded StatusBar
  - clicking clock opens alarms
  - clicking date opens calendar - today selected
  Id: I850732dcca0e65af59ce009aaf9f7ba18bcaf915

- Add onLongClick action to notication clock and date
  - As discussed with ciwrl on google+, LongClick opens DateTimeSettings
  - Moved on-touch color change to superior xml solution, as suggested by
    Andrew Boren <preludedrew@gmail.com> here: http://review.evervolv.com/#/c/3676/"
  Id: I1fae71e347ffcb786227ba0b2651a66f2df35e27

- Add SET_ALARM permission for SystemUI
  If one or more third-party alarm clock app is installed, clicking clock should
  open an app chooser for the alarm clock. However, permission for
  com.android.alarm.permission.SET_ALARM is required to make this behaviour
  work properly.

AICP:
Modified for AICP

Change-Id: I8006e57a953fe0c4be480e0aa27a4c28c672f982