Provide hooks to allow non-javascript execution of guards and actions

[mogsie]

Scion in it's current state executes the content of expr, cond and <script> as JavaScript, and assigns data models likewise. Is it at all feasible to allow for other languages?

E.g. the scion-shell project is not very useful outside academic testing, since it cannot do anything; the guards and actions and so on can't break out of the sandbox.

Comments?