make handlers Atom classes; make engine copyable
simplify standard handlers
update standard handler constructions
only generate a scope key if needed. fix exception squashing.
update the construct node

- create a default engine
- add space for superclass nodes
- update comments
update compiler helpers

This is largely still WIP.

- initializes a new node taking into account any super nodes
- asserts the d_ members
- adds initial read and write dispatchers
WIP commit of instantiation handlers