More advanced (auto) update process

[Xiphe]

The current auto-updater is not flexible at all here's the features I'd expect from a stable version

• enable/disable the whole auto-update process (No network traffic when disabled)
• choose if alpha/beta releases should be included in auto-updates
• choose if BB should look for new updates from time to time (if active check on a ~1h interval)
• have a "Search for updates now" button
• choose if BB should automatically download new updates
• after download of a new update I want a dialog saying "restart now for new update", "apply update when app quits or restarts", "ignore update"
• In all dialogs I want to see a changelog of what happened since my currently active version
• I want a download progress bar that I can cancel