added HUC layer toggle, off by default
recoded, fixed some stuff, cleaned up.  toggle button changes text on click.  thanks Carl
Broken:  error layer.getVisibility

is not a function... but getVisibility is a method of the layer.  not
sure what the issue is.
fixed bug from last week, working now
Merge pull request #131 from marsmith/WATERSMART-350

added HUC layer toggle, off by default