Improvements to tools

- Improved bash_expand() to display lists and tuples not in a python
representation format but like single cmd line arguments.
- added addprefix()
- added move_filename()
- added shellquote()
Improvements for targets

BaseTarget:

- Added "priority" attribute
- Added "out_subdir" attribute
- Renamed "outsuffix" to "out_suffix"
- Improved implementation of get_outfile()

Added "NoOutputTarget" target class.
Improvements for sessions

- Sorted target building by priority
Changed default value of command_indicate of options
Corrected typo
Target names now default to their class name
Module main implementation to execute a makefile
Added __version__ and __author__

.. also imported target.NoOutputTarget
Added setup.py