Remove Swing Look And Feel management

[ghusta]

Not necessary anymore with JavaFX.

See :

• https://stackoverflow.com/questions/2968409/does-javafx-have-a-native-look-and-feel-option-like-swing
• http://fxexperience.com/2013/01/modena-new-theme-for-javafx-8/

Legacy :

• https://docs.oracle.com/javase/tutorial/uiswing/lookandfeel/

For example this is not necessary anymore :

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

Remove also mentions to *.laf.* properties.