[Develop] Starting Frontend-Backend stuff

[Ben Dean-Kawamura]

So I just checked in my first changeset for the frontend-backend stuff.  I
added some generic signal code, and converted error handling to use that code.

I started refactoring util.py and app.py.  Instead of having a module named
"miro", I decided to name it "frontendutils".  This is more descriptive and
we can't name a module miro anyway because it conflicts with our miro package.

I think this new system is going to be really clean, I want able to remove a
couple weird things like the if statement in util.failed that tests if we're
in the downloader or not.  Also, it's much nicer in the unit tests.

Ben