Make sure the Leaflet contribution footer is visible (was moved out of the viewport).
Add navigation to leaflet contribution footer.
Merge branch 'refs/heads/link-about-us-and-legal-on-homepage'
Add min and max zoom presets for map.
Remove hard coded lat/long for Berlin.

Not needed, as the map is not centered on Berlin anymore.
Merge branch 'refs/heads/feature/min-and-max-zoom-263'
Add missing attributes in ownership hash.
Delete duplicate attributes in rabl templates.
Merge branch 'bugfix/missing-ownership-attributes'
Commodity: add models to allow factorization of hard-coded commodities

Add the following models:

 * CommodityGroup: a container for commodities, such as 'vegetable'
 * Commodity: a commodity
 * Translation: polymorphic model that can be applied to any other model
   in order to provide I18n support (currently used for CommodityGroup
   and Commodity).
Commodity: add rake task to create commodities, commodity group and translations
commodities: add controller for json output
commodity: add has_and_belongs_to_many association between farms and commodities