Allow DEMs with projections that are not north-up

[nwagenbrenner]

To do this, one idea is:

1. Read in the DEM in it's native projection.
2. Grab the DEM center point and reproject that point to EPSG 4326 (lat/lon).
3. Make another lat/lon point some short distance straight north of the lat/lon point generated in 2.
4. Reproject those two lat/lon points back to the projection of the DEM.
5. Now you have two sets of points, one in lat/lon coordinates which forms a straight line aligned with north and another set in the DEM projection coordinates which forms a line that is some angle off of north.
6. Compute the angle between those two lines and this is the angle by which the input wind direction needs to be adjusted.
7. Adjust the input wind direction by the angle calculated in 6 and proceed with the simulation.

We think this is all that would need to be done, but this work should be double checked during implementation.