For update commands, pass parent and child concepts to php

Only for update, since we don't seem to need it for the other commands yet.
Use parent and child concepts from JavaScript instead of relation sig

This way, if the modified concept is a specialization, we use the specialized concept for addAtomToConcept, rather than the general concept that is in the relation signature, thus causing editUpdate to work correctly for narrowed relations.
Allow editing also on narrowed relations + Cleanup
Use normalized expression + Comments + Cleanup
Fix editable concepts in slightly hacky way

The more complex definition of editable relations makes the duplicated computations more annoying than before.
Fix: take into account editability of relations
More general getEditableDeclaration

Doesn't work correctly yet for widened interface expressions, as the widened type is used for creating new atoms. It can be fixed by having the type checker return the narrowest possible type, or by computing the types in getEditableDeclaration.
For editable declarations/relations, use declaration's type signature

This works for most cases, but does not respond to narrowing or widening. If we want full support for that, we will need a rather complicated algorithm that will mimic the typechecker and is underspecified at the moment.
a better name for SQL attribute in epsilons.