Promote getEditableRelation to top level

Gives us a bit more horizontal space.
Use narrowing/widening epsilon sequences to compute editable concepts
Simplify getEditableRelation (tested)
fixed getEditableRelation, after comments by Martijn.
Small small improvement of the code of getRelation
Merge branch 'use-epsilons-for-editable-concept'
make conjunct table and relate interfaces to conjuncts