create new font, created new button style, used background for all screens
corrected the layout of the player chooser screen
update the help frame to match the new style
updated the style of overlays like help or dialogs
updated player screen due to the new style
updated the rest of the ui to match the new style
Merge branch 'master' of https://github.com/FAU-Inf2/fly-gdx
removed unnecessary settings, made them platform dependant and corrected the font color of game finish overlay