Develop Rascal shell wrapper with library version argument

[toinehartman]

Develop small rascal-shell.jar that can start a arb rascal version after optionally downloading it.

Note: this probably involves extracting the Maven logic from Rascal to a separate project, so it can be used in the wrapper without depending on Rascal directly.

[DavyLandman]

Note that this used to be part of the std scheme removal, but we don't need this for that. A user can still download the rascal.jar they want and run that.

It might be a nice script to develop, but it does not have any priority right now.