Improve start window

[jakobharder]

• Reintroduce automatic path detection
• Make selection async again
• Path text box should use ellipses and be wider?
• Start window should not be a separate window

[Ixam97]

The start window has been overhauled with 0.6.0 and will see further adjustments.
Didn't follow up with making it not a seperate window and auto path detection. Might think about that at a later stage when 117 compatibility is done.