Investigate on the possibilities of creating an sbt plugin for student commands

[robinraju]

The studentified version of a course repo ships a number of source files along the project directory which are not relevant to the actual course.

eg:

Man.scala
Zip.scala
Navigation.scala
StudentCommandsPlugin.scala
...

It would be nice if we could create an sbt plugin containing all student commands and just add it inside plugins.sbt of the studentified artifact.

[eamelink]

Once #151 is done, this will be feasible.

[eloots]

Note that, with CMT 2.0, once we publish the jars to Maven central, an sbt plugin (for courses that utilise sbt as build tool), such a plugin should be straightforward to implement.