Various changes

-Crate RoF bonus doubled (maximum 20% bonus with 4x8x8, up from 10%)
-Made 50mm cannon default gun if trying to spawn a custom gun that
doesn't exist
-SC no longer compatible with smoke rounds
-SL fire rate increased 33% (now ~25 seconds reload)
-75mm AL clip increased from 6 to 8 rounds
-75mm AL reload increased from 14 to 15 seconds
-100mm AL reload increased from 18 to 21 seconds
-SA can now load HEAT rounds
-Engines now save adjusted pitch, instead of using the value currently
in sound tool
-Fuel drum can now be linked to engines
-5.2l v6 special: torque slightly nerfed, fuel efficiency increased 25%