Updated PixiShader to use standard uniform naming conventions (1f, 2f, 2fv, etc), fixed examples, added multiple shader support, updated Gruntfile.

Updated PixiShader to use standard uniform naming conventions (1f, 2f, 2fv, etc).. Added support for multiple sampler2D calls, allowing multi-texture shaders. Added support for Linear, Repeat, Nearest, Audio and Keyboard textures. Updated all the examples to use the new uniform naming convention. Updated Gruntfile to use the renamed GrayFilter and fixed indexAll in Example 15 to use the GrayFilter as well.