Add self-update functionality

[vadi2]

Requirements:

Grahame Grieve: but I think this app isn't quite the same... I think it should sms the adminstrator when there's an update released, and have a button to download and install

Vadim Peretokin: Yes, I prefer the same Paint.net approach, don't annoy the user right when you want to use the app

Okay so no pop-ups of any kind at the end, just enable a button when there's an update & send an sms (once?) when you find it

Grahame Grieve: y.

Grahame Grieve: once you find it

Grahame Grieve: if there's an adminsitrator

Vadim Peretokin: right