Can urs2sww and other converters be made independant of domain.geo_reference.get_origin

[Nick]

this ticket is about making the run script more simple

It would be very useful if urs2sww were independant of the origin in the domain created.... This stems from the desire to have a build_???.py and a run_???.py. build_???.py would create the DEM and boundary files and needs only to be run only at the begin of the scenario. therefore simplifing the run script

OR

allow the reading in of geospatial_data objects, the addition and exporting to file to be cached.