templates/leaflet_base.html:

Added common dependencies to the leaflet base template, and added
a license header.
templates/hazard_models.html:

Cleaned up a bunch of stuff from the hazard models template.
A ton of stuff has been moved to the base leaflet template.
geodetic/templates/geodetic.html:

Rebased the geodetic template off of the base leaflet template.
gaf_viewer/static/gaf_viewer/gaf_viewer.js:

Cleaned up the gaf viewer to work with the new styling.

There's still a lot of duplication between the gaf_viewer, the
isc_viewer, and the ghec_viewer. I really want to fix that.