Scene text position fixed when non-100% scale

[JohannesMP]

The the Unity Application is scaled to not 100% - either via Unity 2019's new UI Scaling preference or via the Operating system's display settings - The result of camera.WorldToScreenPoint is scaled incorrectly, although only if the camera is that of the Editor Scene viewport: https://i.imgur.com/km7FVSI.png

This change attempts to fix this by moving the camera-to-screen-point calculation to a helper function that when called with the editor scene cam corrects for the scaling offset. It also corrects for the inherent 40 pixel vertical offset that results in text being slifghtly too low: https://i.imgur.com/zr7I4QU.png