-Added thumbnails for thrusters.

-=NEW=-
-help Thruster renamed to Maneuvering Thruster
-Large Ship thruster variants
-Some tweaks.

-=NEW=-
-Added a new thruster called the Oxygen_Help_thruster, which is basiclly an RCS thruster (but works like a normal thruster)

-=Other=-
-The Oxygen thruster that was before now outputs less force (almost half less)