Fixed: Powerup Spawn, Player.Move() and Direction

Lots of fixes:
Powerup spawn fixed, turns out I accidentally set texture = null for
testing and forgot to take it out. Powerups also now add fuel.

Move function was 99% implemented but you forgot to include useFuel()
and the logic was slightly wrong
else if(fuel>=fuelCost)
{
fuel = fuel - fuelCost;
}

not else if( fuelCost >=)fuel

Also direction textures for the player were fixed by getting the last
direction used and using that to draw. This fixes the bug where the
player continues to move by only hitting e.g. down once, but now the
direction textures draw correctly to.