Uses config API instead of bower.json

This swaps out all the references to `this.cpui.paths` to use `this.generator.get('path')`. We're also setting up a default config so that if any of the keys (or the entire `.yo-rc.json` file is missing), the defaults will get injected instead. 

- [x] If I create anything with an already existing module, it exits as soon as I've named the module. I haven't figured out the cause of this one yet.
I mentioned my renaming of that in [this commit](https://github.com/Fullscreen/generator-cpui/commit/34fe256804feff1df224fb1accfc38c15dc40585), but in short I just like that convention because it's obvious at a glance what the context is. I know from reading the docs that it's the `RunContext` object, but for future authors I think naming the context is easier to read.