virtualenvwrapper support, PYTHONPATH

Set sane defaults for `$WORKON_HOME`, `$PROJECT_HOME`, and
`$VIRTUALENVWRAPPER_HOOK_DIR`. But created function and hook to
automatically detect my meta project dir when changing directories and
cd accordingly so that virtualenvwrapper can find my per-project venvs.

Updated and filled out PYTHONPATH.

Added some mucho sexy virtualenv aliases.