Guess UI-Scale on initial start

[rubenwe]

On the initial start of the application, if no ApplicationSettings exist, the UI-Scale for the application should be guessed based on the users system settings.

Most likely the relevant information can be determined from the Screen class in Unity.

[lottehime]

Suggestion for the implementation:

Base UI object scaling from Screen.height / Screen.width dynamically as opposed to using currentResolution or by grabbing from Display.systemWidth / Display.systemHeight.
Alternatively implement CanvasScaler to handle scaling (depends on strucutre of UI objects as to what is more reliable).

If time permits, I will have a read over the source and propose a PR unless project is dead/stalled?