Map should support config-based layers

[jsherrah]

Instead of just using cloudmade tiles that are hard coded into map.js directive, we should use a config file or build config option to determine the intended environment. Thus, we can change which OSM server we're pointing to easily.

[virtualandy]

It does (sort of), just have to change the source of tiles:

    map = new L.Map('map');

    // create the tile layer with correct attribution
    var osmUrl='http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png';
    var osmAttrib='Map data © OpenStreetMap contributors';
    var osm = new L.TileLayer(osmUrl, {minZoom: 8, maxZoom: 12, attribution: osmAttrib});   

See getting started with leaflet on switch2osm.org for more.

Edited this issue to say "allow config-based properties to determine source of layers".