Print out the modules that led to a binding during error reporting, but
only if there's >1 module (otherwise it's just noise).  The format is
Some normal messaging about the fact that something terrible happened
at <the normal source> (via modules: A -> B -> C)

So, for example, exposing something that isn't bound would show up as:
1) Could not expose() Foo, it must be explicitly bound.
at FooExposerModule.configure( (via modules: ParentModule -> FooExposerModule)

.. and a duplicate binding would show up as:
A binding to DuplicatedThing was already configured at ModuleA.configure( (via modules: ParentModule -> FooModule -> ModuleA)
at ModuleA.configure( (via modules: ParentModule -> BarModule -> ModuleA)

All the tests passed as-is (because this is just new information), so I made a bunch of tests stricter to explicitly look for this new information.

I also cleaned up some other errors regarding scopes & some other stuff.
Created by MOE:
20 files changed