write test for Invocable
refactor module context handling
refactor: Require object
refactor and a very important test case
module.exports - impl interface
module.exports - impl interface
require.impl() suddenly works!
refactor Require
ModuleSpec: use separate Require instances for different cases. Now the suspicious require.impl() breaks again!
refactor module to use only one ScriptContext
require.impl() works for real
rm some extra code
refactor, rm unneeded tests