Extend readonly proxy support to cover Set and Map

When an RA rule wants to access game state, it is accessed via a
readon;y proxy. The proxy handles methods for arrays only and fails
when the rule tries to access methods of other classes (e.g.
JobIDMap contains sets).

SugarCube supports arrays, sets, maps, the date class and generic
objects in the game state. Therefore the proxy has to be extended to
support Set and Map classes too.