Updater progress

* Changed to using an INI file for expandability
* Now downloads the installer specified in the INI file
* Fixed behaviour bug with bluDownload not being able to download more
than one file

Will work on the update / changelog UI next.
Download updates, provide UI to launch

* Updates can be downloaded ("Update.ini") which then fetches the changelog ("Update.html") and installer ("Update.exe"). An "Update!" button shows in the UI which shows a form with the changelog and a button to "Exit & Update" which will launch the installer which will automatically install and re-launch the app.

Also:
* Fixed installer bug with installing over an existing installation
* Added custom Welcome / Finish images, improved messages
* Installer clears the old update info to avoid updater confusion
* Added `/UPDATE` to the installer to skip all screens but the install files