* d2player/game_controls: Refactor HUD into it's own class
game_controls slowly becomes a superclass that does too many things.
So move HUD into it's own class. This is the first step of getting the
renderer out of game_controls (#798)
* d2ui/tooltip: Allow background box to be disabled
* d2ui/tooltip: Make GetSize() a public function
* d2player: Move const from game_controls to hud
* d2player: Fix missing entity hover tooltip
