Better use of ArcGIS Server Geometry Service

Instead of relying on client side Dekho code to measure length and area, Dekho now uses the ArcGIS Server Geometry Service to convert between units for all length and area calculations.

Length calculations use the geodesic property for calculations when the output coordinate system is geographic. This means calculations are based on the ellipsoidal shortest path distances between each pair of vertices in the polyline.

Area and Length calculations can now be performed in coordinate systems different to the map default.