Removed image editing code

 - Rasterisation is beyond the scope of this project
 - Was just "clear" and "pset" anyway
Corrected big endian translation
Cleaned TGA loader

 - General code cleanup
 - Moved image flipping/color channel changing into
   main image functionallity. Loader uses it as post
   process
 - Lots of simplifications
 - Read rows of pixels instead of individual ones
Minor cleans in the bpm and bmp loaders