Extract script commands to take an source locator instead of direct
content.
Create ScriptModule from ScriptSource not ScriptCommand
Checkpoint, script modules nearly working
Need to adjust the containment and lifecycle of static context,
and make a per classloader single cache of modules
Checkpoint with Module and module context reworked.
Passing all core tests - still a bit to go.
Reworked Static Environment and Modules split out into their own caches,
and distinct from the shell environment.
Wrapped modules into reference counted handles.
split prefix out of module definiton instead use the namespace table.