Change Mixpanel calls to NPAnalytics class

Change to useing NPAnalytics for analytics logging. Also create a short
hand method for tracking and use that instead.
Clean up remaining 'NPBoston' references

Change remaining NPBoston references to NovProject. This is a cleanup
task from when the project changed names.
Remove stray reference to Mixpanel.h
Change NPAnalytics to class methods

NPAnalytics used the singleton pattern but it was not needed so this
changes to using all class methods.
Remove old singleton references in NPAnalytics