WIP Variable-ize "Certificate of Achievemnt" text

@dianakhuang & @singingwolfboy - here's a WIP PR for variable-izing Certificate name text.
There are a couple of things that I'd like help with:
- Internationalizing the variables that are set
- Figuring out what to do about dashboard.html, as it doesn't reference the course object when the word certificate is used.

FYI: @shnayder & @jrbl