General changes + easter egg

- Changed `getLangValue` to a better solution
- Updated the `About` form
- Fixed highlighting `@` macros
- Fixed `scroll past EOL` option
- Fixed the `You must restart the environment (...)` message in settings
- Added a `-sconst` compiler switch
- Added a small easter egg :-)
- Small change in `readme.md`
New demo

- Added new demo: Mandelbrot
- Fixed VM and compiler paths in demos