Context switching when executing a representation.

[bruno]

Some representations might require that threadlocal state is restored to the situation as it was when handling the request.

E.g. the 'current' restlet application, context, ...

This can be important to do such things as resolving URIs within the context of the original module.

Or maybe representation implementations should be written in such a way that they don't rely on this.

Needs further thinking.

[mpo]

beyond 0.4 scope