Added color filter

Use case: Set all the pixels of an image to a color, for generating
fast background colors.
Fixed the haze and levels filters under iOS 7.0.
Allow matching existing alpha value in color generator filter
Put solid color generator overloads back, improve performance
GLSL fixes
Merge pull request #1024 from jjxtra/master

Solid color generator filter alpha option
Fixed some poorly-named macros that were conflicting with other frameworks.