Changed interface in get_val_on_key.  If have nested containers, will
return the nested container's reference object rather than internal
val when call get_on_key.
Began adding endpoint variables back in.  Also, fixed a bug.  All of
the externals were trying to create text variables and using classes
that did not exist to do it.
Variable constructors no longer take a variable name.
In single-threaded, delete the from the value directly, rather than
from a wrapped value.
For nested containers, return the reference to the container, rather
than the internal container.
Renamed insert method on lists.  Updating in emitter.
When assigning on a map's key, if the map does not have a value on
that key, then we should add an element in the map with that value.
Maps should return dicts when dewaldoify.