SW-98. Split setup into native and tree implementations.

Implemented native setup. Added use appdirs.py. See
http://github.com/ActiveState/appdirs.
Added openvisualizer.conf. It is useful for configuration, but including it
now so we can use it to determine the kind of installation of OpenVisualizer.

Only import pathHelper.py at app startup if used runs app in in-tree
development mode. THis file is not included in the setup-based distribution.

No work yet on the tree-based setup.