Bug 917946 - Add Gaia-marionette tests for the settings app 

This is a proof-of-concept / request for feedback regarding this approach to writing js integration tests.

It includes a `Base` app object which other app objects can extend in order to inherit common functionality.
It includes a starting point for a `Settings` app object, as well as a `BluetoothPanel` region object.

Not having a lot of experience writing object oriented Javascript I may have done some things that are not ideal, so I am eager to hear feedback/suggestions. I will add specific comments to the pull request in areas where I am unsure about what I did.

Pinging @lightsofapollo and @gaye for comments, but any and all feedback is welcome.