Updated to v1.6

- Added container objects.
- Added color themes.
- Renamed almost everything from "screen" to "window".
- Renamed the "Slider" object to "ProgressBar".
- Renamed most "show" functions to "draw".
- Completely changed event handling and displaying of the objects.
- Removed AddOn support.
- Bugfix: Elements of List-objects couldn't be changed. (This time it
does work!)