Introduce AlertTypeNone, enableDebug and forceAlert

This PR enables:

- AlertTypeNone: in our case we don't want to have an alert for Patch update only for Minor and Major
- setEnableDebug: this logs the json & URL used to connect to the iTunes store. Handy if you are tracking why it can't be find a version
- setForceAlert: sometimes you want to see the alert regardless what your app version in the appstore is. This allows you to force this. Handy if no version are in the Store yet.