Refactoring DeviceProfile

-> Pulling out the parts of device profile which can (and need to be)
   initialized and accessed without access to an Activity context,
   ie. the invariant bits.
-> The invariant bits are stored in InvariantDeviceProfile which is
   initialized statically from LauncherAppState.
-> The DeviceProfile contains the Activity context-dependent bits,
   and we will create one of these for each Activity instance, and
   this instance is accessed through the Launcher activity.
-> It's possible that we can continue to refactor this such that
   all appropriate dimensions can be computed without an Activity
   context (by only specifying orientation). This would be an
   extension of this CL and allow us to know exactly how launcher
   will look in both orientations from any context.

Sets the stage for some improvements around b/19514688

Change-Id: Ia7daccf14d8ca2b9cb340b8780b684769e9f1892