Start migrating the PBM support from bitarray.c to the new Image API.
Add bitarray/c and bitarray.h for reference. [to be replaced with image.c image.h]
Migrate the PBM code from bitarray.c to the Image API.
Add tests for the PBM functionality now in image.c.
Add previous bitarray tests for comparison with new image tests.
Remove bitarray files as functionality is now in image.c.