This (large) patch reintegrates the bb.make module into the bitbake executable.

This (large) patch reintegrates the bb.make module into the bitbake executable.
Said make module has been factorered out back in the old days when we had two concurrent
oemake implementations which were in need of code sharing. Nowadays, there's no
more use of a seperated make module and in fact the split has always been a bit
artificial.

A brief overview of the changes:
 * create utils.py which contains three unbound functions for comparing versions
 * create a class BBConfiguration that holds variables which were formerly living in make module scope
 * make functions use the BBConfiguration instance that lives in BBCooker instance
 * move functions into the BBCooker class, adapt them to work as class methods
 * integrate the function of the bbread executable into BitBake; use it with option '-e' and (optionally) -b
 * remove make.py
 * remove bbread
 * adapt the shell module which has been using the make module directly