Minor improvements like natural sorting and fixes

• natural sorting of file names
• hide boxes is visible as checkbox option
• transparency sliders
• fixed on_activate on file-change

Egui only

• We show the image also using Egui.
• The menus do not float but are on the left or right of the main image.
• The dependency to Pixels has been removed.
• The interface between the frame-buffer and the rest of the app is clearer.

Reduced CPU, fixed security issues

v0.1.1

release 0.1.1