SW-98. Create openvisualizer package to avoid global namespace pollution.

Installation of OpenVisualizer requires this refactoring. Packages like
openLbr should not be top-level, but rather sub-packages of openvisualizer.
Created lib directory to contain openvisualizer package and sub-packages.

Also renamed treeSetup.py to setup.py, since the tree-based approach will be
the default.
SW-98. Continue to set up use of openvisualizer package.

Updated nativeSetup.py for openvisualizer package.
Also, change config_site_dir default in appdirs from /etc/xdg to /etc.
SW-98. Move modules to openvisualizer package.