New polygon to represent "buildings" geometry and hydrology Merged

This polygon would allow the user to set the roughness, porosity and flood threshold level all within a single polygon object - negating the need for many overlapping ones. Furthermore, the user is able to set the runoff characteristics for the building. These will be generated as per subcatchment with a single runoff surface and routed to the specified location. Additionally, the user has the ability to set a capacity limit, any flow above this will be capped from entering the 1D network. Instead the flow will be passed out on to the elements surrounding the building. Much as the building boundary now acts as a 2D line source for any flow in exceedance of the capacity limit. Models should now far more accurately represent localised flooding on the 2D and route appropriate limited flow into the 1D network.