Improve interface for retrieving hidden parameters from Modules

[meissnereric]

It's a bit difficult (and not obvious) how to get the parameters of a Module out of the InferenceParameters. Right now you have to do something like infr.params[m.y.factor.kernel.lengthscale].

Having a method on the Model class that retrieves all components including internal module components might be handy for users.

[meissnereric]

Tagging as a bug because it causes weird, unexpected behavior when a user passes the uuid of a Module parameter into it's outer model and it says it doesn't exist.