Added native functionality to create a color layer.

Added a new layer that can draw a specified color and specified
alpha. This will replace creating a dim layer and allow any colors,
not just black, to be set for this layer.

Test: Added tests to Transaction_test.cpp to test with a color
      and a color layer with alpha.

Change-Id: I00a38d1bbc01093026f088c3347454281bdc2b8c