Add final project logos

This includes
- The squared-version logo
- App state icons (app.ico, app.png, app_error.png)
- ico has alpha channel and contains 16,32,48,64,128,256,512 sizes
- svg is minified with https://jakearchibald.github.io/svgomg/
- png files in various sizes (as ico)
- two header files for the README.MD
- the illustrator resource file

Author: kalaschnik