Update app version count for existing users when they upgrade to newer version

[amarkulo]

It would be nice feature for user tracking to be able to track users that have upgraded from one build(version) to another, how many is on new one and how many left on old one, how many upgraded, etc.

Right now counting is the same for both, so for each new version users registers as new users while old one from which users have upgraded stays with the same count, it doesn't decrease.

[gorkem-cetin]

@ar2rsawseen checking this and not sure if it is something doable on CE without a lot of effort, so need your comments.