I added the tools we already have. I slightly modified HSCSession to optionally take a base url, which one can use if they have access to non-public data.

I'm thinking we should make a single class (StampFactory?) that can fetch images from any of the surveys. We could keep the individual helper functions in tools, since it may be easier to call them sometimes, but it'd be nice to have a class that unifies them all into a common API... what do you think?