Run the grader and the Broadcaster as separate services

[lhchavez]

While it is convenient to have them both run in the same service, forcing a restart on the Broadcaster every time an update to the grader is made is inefficient, since all long-lasting websockets connections die and need to be brought back up. This can be solved by deploying both as independent services (and probably even forego the need for running proguard and storing the .jars in the repository!).