Use cowboy for rest
Created by: gorillainduction
Migrate all rest endpoints from using Mochiweb to using Cowboy since the Mochiweb endpoints cannot run under otp-21 and making them do so would be major surgery anyway.
In this PR the Mochiweb endpoints are still present, but opened on a different port for side-by-side testing.
A future PR will remove the dependency on Mochiweb completely.