basetag() returns name of ConstraintRule without node id.
Check on whether Rule is principal are now done through basetag(), it's sufficient.
Add part of future analysis: CallerTableBuilder.
Step subclasses are meant to be immutable and stateless.
The state is now encapsulated in Effect subclasses, which can be combined.
Correspondingly, schedule now produces streams of effects.
Certain compromises have to be made: for one, it is assumed there is only one
project open and it is a MPSProject. Feedback is only reported to the messages
view and the view itself is not yet integrated into the main messages view.
Grigorii Kirgizov