Prevent the add tree search from submitting form

When the search <a> was changed to a <button> it started trigging the
submission of the search form. Adding "return false;" to the
onsubmit of the form prevents that.
Add reverseGeocoding to geocoder.js

Allows the add tree client code to lookup the address for a new point.
Reverse geocode new plot location Fixes #670
Merge pull request #688 from jwalgran/topic/reverse-geocode

Reverse geocode new plot location Fixes #670