remove dead files
make distinction between module and expression nodes
make distinction between module and expression nodes
make read and write handlers public
use a scope key instead of a scope name

This is more flexible and eliminates the possibility of name clashes
with imported library enamldefs which are embedded in the widget tree.
update the compiler code generation
add a node class which stores the tree type structure
update compiler helpers for new compiler code gen
wip commit for metaclass updates