The script engine is given a better binding mechanism and a reflexive access

Better binding mecanism : formerly done through the default SimpleBindings
shipped with the API, it now goes through a custom IBindings class
which uses the bind method of the interpreter instead of simply
making the bindings available as a Map.

Reflexive access : the script engine is made available to itself
through a bound variable "engine" of type javax.script.ScriptEngine.
This will allow "variable injection" i.e. programmatic redefinition
of variables, among others.