Add creation of new use case

This adds the necessary pieces of Ember, including controller and
routing, to request a spreadsheet copy and create an ember UseCase
object with the submitted information. It also adds the start of the
express routing to handle saving the new use case.

Still need to implement saving the created use case and spreadsheet id
in a json config file in the .iago folder.
Start config helpers for config file persistence
Simplify config helpers, add overwriteConfig option
Use config helpers in load.js, add configPath to config
Save newly created use cases, add path centric config saving
Convert file name spaces to dashes when saving

File name spaces are not converted when a file location is given instead
of a file. Probably need to use some RegEx to get the file name if given
a file location, and convert those spaces to dashes. The problem with
using the entire path is that any path containing spaces would no longer
work.
Return 409 if creating a use case that already exists
Refactor useCases controller for additional readability