Updated the footer

Leaflet in the footer was hyperlinked to the older website which is currently not available. Updated to the current one.
Update
Added the leaflet beta url
Deleted buffer files
Added the image upload control
Leaflet controls added to modify images
Added rotate and distort functionality, organized content
Added documentation
Synced the fork with the public lab fork
Merge branch 'master' of github.com:publiclab/mapknitter