Add KML vector layer to map with popup thing
Map updates: Make fixes for OpenLayers 2.13.1; refactor layers

The upgrade to OpenLayers 2.13.1 broke some things, so it required some code
changes. I took the opportunity to refactor the way layers are constructed and
moved them into their own JS file
Move the to_kml method to LakeManager; make it work with bboxes
Add tests for the to_kml method; split Photo model tests into module