gregreen
Expand SFDQuery to include mask and other data products
This PR allows users to query the SFD bitmask as well as all other SFD style data products stored on the Harvard Dataverse under the same DOI. The bitmask is forced to use order 0 interpolation to avoid violating the bit quantization. It appears that the padding done to the data to try to handle distortions at the Galactic Plane was not as successfully applied to the mask data product, leading to some artifacts near b = 0. However, it appears that this is a faithful reproduction of the values in the FITS file and the WCS header and so I am not really in favor of changing it at this level. A lower level change to better handle the distortions etc. would be preferable. In total, I think making these data products, especially the bitmask, is extremely valuable.
I should say, I did not make any effort to enable this functionality from SFDWebQuery.