IDE build managent (front-end for the build system)

[kohlhase]

Once the build system is working again, and we have the JEdit archive manager (see #378) we should have a JEdit front-end to that which acts as a build manager for the local fragment of MathHub. This should give access to the build queue allow to trigger build requests, and show the build status (built, needs-build, deps-stale,...) of the files currently under consideration by the user (open in JEdit)