Rename backboneAgent to agent

Here's a simple but nutso PR, that i'll probably merge pretty quickly because I hate looking at it.

in a nutshell its `:s/backboneAgent/agent/` 

why did I do this. well - we inherited `backboneAgent` as a term and I want to do away with the old and introduce the new. Also I feel like agent is a nice term. Maybe **spy** would be cooler or **debug** which ember does. but alas. agent is generic and has certain charm. it's kinda a spy, right...

![](https://www.statesidestills.com/prodimages/goldeneye_cast_36532l.jpg)