Closed Feature: Add Convolute method [14796]

Add the Convolute method as suggested here
http://writeablebitmapex.codeplex.com/Thread/View.aspx?ThreadId=236374&ANCHOR#Post528218
 
Todo:
The alpha value should be preserved.
Use rectangular array as kernel parameter to avoid kernelwWdth and kernelHeight parameters.
Optimizations.
The values should wrapped at the borders.