Added Crashlytics

Integrated Crashlytics without all the baggage in the other pull request related to the changing of FileLogger calls to WPFLog*. 

I also added in a check to the modified build script that I got from Cheddar iOS(https://github.com/nothingmagical/cheddar-ios) that only attempts to run the Crashlytics related additions if it's a release build. This way if someone wants to build and test the app locally they won't need Crashlytics. Crashlytics is required though if we want to build a release build for the app store.