Bug and UI Fixes

-Goblins should no longer stay standing after they die sometimes.
-You can now see which hotbar is selected in both your HUD and inventory.
-When a goblin dies, they now have a chance to drop bones.
-When a goblin dies, their red dot now disappears from the map.
-There is now a pop-up when you start a game that explains what to do for that gamemode. (Known bug: in multiplayer, clients will see both game mode pop-ups.)