First cut of a toggleindy gvm command.

The script updates the currently selected groovy install to use the
indy jars.  In particular, it makes the $GROOVY_HOME/lib a symbolic link.

The old lib directory is renamed "$GROOVY_HOME/lib_nonindy", and it
creates a new directory "$GROOVY_HOME/lib_indy" containing links to
the original jars, with indy jars replacing the non-indy jars where
appropriate.

The script toggles between indy and non-indy by changing the lib link
to indy or non_indy as appropriate.