Add unit test for gdsHash.

This should help detect any changes to the gdsHash functionality, like
those observed with the TDM on the thredds test machines.
Restore tests disabled while testing gdsHash.
Improve return of all data for sweep(s) for CF/Radial.

Pad out the data so that the returned arrays are rectangular. Also add a
test from NCAR S-Pol data where the RHI sweeps have varying amounts of
gates in a sweep.