Payment Reminder Dialog

Premise: We want 3rd party devs to get paid for their apps. Traditional open source users get pissed off about paying up front for things. We need a way to provide a payment "time bomb". A kind of reminder to pay. It needs to be easy (one click), in app, secure, etc.

We should create a standard Payment Reminder Dialog that does the following:
* Provides a standard message and layout so that users become familiar with the dialog and trust it's origin
* Ties into elementary accounts, specifically for payment so that users don't have to enter payment details into a dialog from an app they've never heard of until a bit ago.
* Features a simple method to choose a payment amount from "Never show me this dialog ever again" to whatever you want to pay.
* Knows if a user did already pay for this version on any of their devices and doesn't bug them again (once again, elementary account).
* Only reminds someone to pay if they actually use the app fairly frequently. Not just number of times (you opened it twice!) or length of time (it's been a month!) but actually, "Hey you seem to use this app at least once a week".
* Knows the difference between a major update and small release and reminds users to keep paying when a major release comes out to ensure more major releases are made.