Make credits configurable on Stanford CME

* Assumes cert_data stanza now has additional "CREDITS" subdict, with a
  key "COUNT" and a key "TYPE". These are interpolated directly onto the
  certificate.

@stvstnfrd, please. @caesar2164, fyi.

My hope, @sarina, is not only that this will help us, but that it will make the cme template marginally more useful to members of the open source community.... (But firstly it helps us by letting us support courses worth lots of different credit values.)
 `ccount` and `ctype` are horrible variable names, as a translator with no context, I can't make heads or tails of what the variables mean. I also don't know what the first part of the sentence means.