gui-refactoring
GUI classes revamp part 3
rebased
fixed slider
Merge remote-tracking branch 'origin/gui-refactoring'

Conflicts:
	core/src/main/java/de/secondsystem/game01/impl/gui/GUIButton.java
	core/src/main/java/de/secondsystem/game01/impl/gui/GUIElement.java
	core/src/main/java/de/secondsystem/game01/impl/gui/GUITestState.java
	core/src/main/java/de/secondsystem/game01/impl/gui/GUIText.java
	core/src/main/java/de/secondsystem/game01/impl/gui/InputText.java
	core/src/main/java/de/secondsystem/game01/impl/gui/Label.java
	core/src/main/java/de/secondsystem/game01/impl/gui/MemoText.java
	core/src/main/java/de/secondsystem/game01/impl/intro/MainMenuState.java
	core/src/main/java/de/secondsystem/game01/impl/intro/SettingsMenuState.java