MAP/OSM : Add tile cache system

[Th3NakedMan]

In order to use less gps data transfer the app should embed the map of the artistic zone route (parcours artistique).

Specification of the tile cache system (draft)

• The tile cache will only be available around the artistic zone route.
• The tile cache should be easily changed for another artistic zone route
• ....

[d-j-a-y]

TIPS

• imgcache.js --> https://github.com/chrisben/imgcache.js/
• Zoomable image with Leaflet : http://build-failed.blogspot.fr/2012/11/zoomable-image-with-leaflet.html