Loupe 50.alpha

- Add a specific error message when loading the image file fails. Usually when the file does not exists or there are no rights to access the file.

- Fixed image navigation overlay controls conflicting with always visible scrollbars.
- Showing wrong mime type in error message if the file ending for an image is wrong.

- Don't allow endless zoom out
- Only allow 4 integer digits and 2 decimal digits. That's what's actually respected by the input at max.
Git-EVTag-v0-SHA512: 97a8178fe970f7ee3640ad26f2ff2b59fefe6ba2a740500e4553429735d220de843bea63a6dea98c6da3abd8cb1b24d4c6bfca39595dae5054ebcb1100221ee4