Override build number

We have been using the crash reporter for a few years, with our own client side for sending data. We switched to the Official unity integration and have lost one feature: the ability to control the build number.

The current client code uses the bundleVersion, but this isn't enough when working with multiple builds sent to the stores. For example we sometimes have several beta builds queued and tested live by users and need to have the full build build information available in the crashes (i.e. on IOS it could be the build number / CFBundleVersion).