Update sbt version

[jpolchlo]

Building this project on a clean environment sprung many traps that were clearly hidden by running on an environment with a pre-populated ivy cache. This project is dearly suffering from being on an old version of SBT. This should be remedied at the first opportunity.

Also, the src/sbt convenience wrapper should be updated to a new version as well that does not point to decommissioned repo endpoints.