UI improvements

[C0rn3j]

The UI could use the following improvements:

• Make the continue/install button disabled until the checkmark is pressed instead of letting you press it with a warning
• Move the quit button to the right corner, or otherwise away from the continue button. Maybe just make use of the classic X button on top right?
• Show version somewhere

[mikeslattery]

I can do the first 2 bullets tomorrow. The 3rd will take longer as it will require me to change my release process. It's not a big deal to do time wise, but I have a lot of other priorities.

[mikeslattery]

Will not start on this until after #10