This introduces a new fullscreen controller
which uses NSVisualEffectView for it's background
and the icons that are used throughout the rest of
the macOS user interface, hence making it more
consistent with the overall look of VLC.
Additionally the new fullscreen controller is
resizable and, as it already used to be, can be
move around on the screen.
The user interface is now described in a interface
builder file (xib) instead of doing everything in
code. This allows easy usage of autolayout, which
is heavily used to allow adaption of the
buttons/sliders depending on the panel width and