Unique mission icons, trim mission image files
Merge remote-tracking branch 'origin/master'

Conflicts:
	saan.js
Update to-do
Interim step - zooming default layers
Layers turn on/off based on zoom

Layers are also now stored in one of two object literals: majorLayers
for those that are always on, or minorLayers for those only on at more
zoomed in scales.
Tidying up
Merge pull request #12 from ldnash/master

Merging changes from master