windowmanager: Add support for blur effects

  * Support for blur layer on the lockscreen
  * Additional code for blur-behind and surface-blur has
    been removed from this commit as it is not in use.

  * Original work by CodeAurora / Qualcomm
  * Contributions from:
    - Steve Kondik
    - Danesh Mondegarian
    - Roman Birg
    - Clark Scheff
    - Michael Bestas

Change-Id: I6285905a4e3c00dfb5471876d0cfb16b4b4e9893