Added routing over sidewalks in rendering_types.xml and routing.xml

The sidewalk tag is a commonly used tag in osm to indicate whether a road has a sidewalk:

http://wiki.openstreetmap.org/wiki/Key:sidewalk

However, this tag was not included in osmand map generation. I think it would be a useful addition for pedestrian routing. I gave a road with a sidewalk the same priority as a footpath (1.2), and included a slight penalty for not having a sidewalk (0.9).
tag=sidewalk mode=amend makes sidewalks available for routing