Removed the rocket launchers to drop the ore requirements and to make the unlock level to 12 and not 15

Took away the 4 big thrusters underneath by adding 6 smaller thrusters (4 for forward acceletation and 2
for break controll/ reversing).
Added 2 more thrusters on both left and right side to improve the sliding.
I'd also remove the upper dead weight, thought it was in the way, added a smoother plating, makes you see more a head
than you did before.

Changed the name from MXII-Sparth to MXII-Sparrow.