Image degradation

I added some code. The pango rendering works perfectly now. Also 1 pure image and 4 partially erased images are created per character.
The degradation has been chosen to suit the code that clips matraas. The only degradation seen is a vertical white strip overlapping certain characters.
Hence the same is done while generating training images.

[1] http://code.google.com/p/tesseractindic/source/detail?r=41