* Implement new content display system.
* Add @FunctionalInterface annotation to displaytools interfaces.
* Use static factory method to create Builder with contents.
* Use T for generic type since it's static method.
* Rename Builder#display to show and require CommandSender.
* Rename package from displaytools to display.
* Move DisplayHandler impls into their own package.
* Overload ContentDisplay#forContent with defaults for list and map.
* Pass CommandSender to send command.
This system is much more versatile when a single ContentDisplay instance
can be used for multiple players.
* Rename ContentDisplay#send to #show.
* Split DisplaySettings into separate classes.
Co-authored-by: Jeremy Wood <farachan@gmail.com>
Ben Woo