GML limit dimensions of coordinates

[crrattner]

If 2-D applications are using WFS transactions in conjunction coordinate transformations via Proj4js library, they can get in trouble with z-coordindates generated by transformation. Because the GML writer than generates the GML coordinates tag with 3 coordinates. If your data base backend can't handle this, the transaction will fail. To solve this it would be helpful to limit the number of GML dimensions per option.