Frameworks: rework navbar and statusbar transparency/color handling (1/2)

All current implemented versions of nav and statusbar transparency
which are around are not really perfect and all have downsides. After I saw the
implementation from Romanb (thanks) I got an idea to solve especially
the problem on keyguard without forcing the user to set for keyguard
seperatly a transparency to have a good result. Main problem is that
aosp does not allow to overlay the navbar with a shadow.

This commit does:

- introduce central TransparencyManager (thanks Roman)
- introduce a layerDrawable with a ColorDrawable as overlay and underlay
  to get consistent results on keyguard to show the shadow
- introduce a overlay to animate the navbar shadow like the PIE background shadow
  when the user is not in expanded mode. So the user get the whole screen darken (or colored).
- get complete rid of backgroundalphadrawable class
- allow colorize of theme (theme engine) navbar/status bar background changes
  reset to default shows as usual the theme without manipulation
- expand the custom background area on lockscreen behind the statusbar
  (navbar AOSP does not allow)

- default wallpaper and full transparent mode is now completly consistent and nice
  looking on every possible setting.
- full color lockscreen reflects the color now behind the navbar
  to imitate same behaviour like the default wallpaper on lockscreen. As well
  now consistent and nice looking on every possible setting.
- lockscreen background image mode is the only one where a 100% consistent solution
  is not possible due that the image is always smaller on lockscreen (not expandable behind
  navbar) and I do not see a good way to put in the underlay a partly image in a nice way
  ...to avoid weird transparency draws the transparency on navbar
  is set to the chosen lockscreen background transparency as long the lockscreen transparency
  is smaller then the navbar/statusbar transparency. Todo: notify in settings the user about
  the behaviour change so that it is no surprise.
- add multiuser compatibility to serveral vars
- margin fix on lockscreen
- hide statusbar on lockscreen on expanded or autohide statusbar mode
- add option to unlink colorizing on apps
- optimizing and a memory leak fix
- cleanup

Change-Id: I22ccfc5d3fff58b266848b2e0983435094ba6847