Cyclosm

This branch adds the cyclosm style for preparing a tile server.

It introduces a new variable: style, which indicates the style of the map tiles (so far, osm-carto, cyclosm, but more to come)

Based on the value of style, the mapnik xml file is changed + all auxialliary files (symbols, patterns, etc.)

Note that for instance cyclosm can also display a hillshade raster and some contour lines. The automatic import of these data is not covered by this role. There is a README in files/styles/cyclosm.style/ that explains how to prepare a cyclosm tile server with or without these files.