Only prevent default action on right mouse click

Preventing all default actions in the viewer prevents
standard widget actions from working. Instead check button
clicked and only suppress default for right click.
Add basic search interface

Add interface to allow user to interactively search
for documents in MongoDB. Search results are updated
dynamically as search terms are typed. The user
drags the row they are interesting in onto the map
to add a layer.
Merge remote-tracking branch 'origin/query-interface'

* origin/query-interface:
  Add basic search interface
  Only prevent default action on right mouse click