Updated reflective finding of declared vals in Bundles.

A while ago, I added a check that elaborates the declared fields of a class and examines whether methods share names with fields to determine whether they are `val` accessors or not (along with other checks, like arity).

This made parameter-less methods returning instances of `Data` work inside modules, but issue #179 brings up the problem that this won't work in a `Bundle`. In order to reduce the redundant code, I thought it might be a good idea to factor out the generation of a list of methods categorized as `val` accessors into another object's method.