Add rgbsplit0r plugin

[namikiri]

One more effect which is popular in the web. This plugin allows you to split the video into its RGB channels and shift them across X and Y axis.

See the examples: before and after.

// This is a correct pull request, thanks @jaromil for explanation. The older one can be closed.

[d-j-a-y]

@namikiri Nice one ! i planned someday to write it ;-)

One suggestion,

• double the amplitude of H and V split distance parameters, to have the ability to move back the red channel and forward the blue....

example for inst->shiftX :

• '0' red channel full back,
• '100' normal,
• '200' red channel full forward.

[namikiri]

@d-j-a-y thank you for your suggestion, I'll include it in the next pull request with some other improvements! :3