NOTE: Task only necessary if we launch this as an A/B Test
####Background
We are planning to measure if we saw a 50% increase in app menu donations as measured by A/B test or pre-post analysis after moving the donate option as a part of Navigation refresh part 1.
####Task
[] Create a data controller in WMFData which outputs whether or not the user see the navigation changes as a whole (50% see changes, 50% do not)]
####Engineering notes
Consider if this will be wrapped up in an experiment or not (lean on current WMFExperimentsDataController for assigning and persisting buckets).
1. Add new navigation experiment enums to `Experiment`, `PercentageFileName`, `BucketFileName`, and `BucketValue` enums in WMFExperimentDataController.
2. To assign an experiment (we'll want to call this somewhere in the app launch sequence), call something like `try experimentsDataController.determineBucketForExperiment(.profileNavigation, withPercentage: 50)`
3. To check experiment assignment (for example, add this check before adding the profile button to Explore), call something like `if experimentsDataController.bucketForExperiment(.profileNavigation) == navigationProfileTest`