add dynamic scoping support (aka "context" vars)
get_dependent_terms, work in progress
Add Actor.inject_context. Actor.call now takes a list
change Actor.call and add Actor.apply. Matches javascript
add Actor.block and Actor.restart
Make sure module branches have an (empty) output
fix null ptr deref inside stack_restart
add Actor.dump
remove Indexable type as it was half-baked. Fix crash on "1[1] = 1"
fix code migration, it wasn't working on Term.type
new file migration.cpp
Rename the migrate api to be more clear. Add struct Migration
add a migration test, chasing an elusive bug