Removed the CoqTopIdeSlave.restart method

coqtop is started on demand, so it can be "restarted" by simply killing it
and then trying to communicate with it
Reworked the Coq editor jobs to use the new basic job infrastructure
Added a text field to the CoqCommand class
Added a common base class for StepForwardRunner and JavaStepForwardRunner
Use the CoqTopContainer as the scheduling rule for CoqJobBase subclasses

This commit also moves some of the shared Coq job classes out of
JavaEditorJobs and into CommonJobs
Removed the CoqJobBase.container method

The method has now been replaced by an additional constructor parameter