Got rid of session.py and base.py

.. and moved code to target.py to remove the clunky code sections that
were necessary to work around the circular module reference.
Corrected locking in PackageDeliverer
Renamed option force_fwd_slashes to force_fwd_slash

And added two methods to print output sections for targets.
Filename generators are now descriptors

Also added TargetOut generator
Implemented BaseBuilder

and renamed Builder to CommandLineBuilder. Implementation has changed to
adapt to the new base class "BaseBuilder"
Added BuildException.more_info()
from make.target import *
Added lazy bash expansion

and changed implementation of makedirs(). sort_targets() was added.
Added README and COPYING
Example C Project buildable with Py-make