TANK ZERO v1.1 update

Changes:
*Added pause menu;
*Improved VERSUS MODE (about them below).
*Improved control on gamepads;

VERSUS MODE changes:
*Increased reward for killing enemy tanks by 2 times;
*More money is now given for killing heavy tanks instead of the same amount as for light tanks;
*Players passively receive 5$ every second;
*Bonuses are spawning in the arena;

Fixes:
*Fixed tank reset when exiting to the menu via ESC;
*Fixed black infinite screen of all players in multiplayer when a mission fails;