[New Feature] FLH based on OpenTopped transport body direction

[Thrifinesma]

Description:

If a OpenTopped transport has turret, the AlternateFLHX will be based on the turret direction. To deal with this, introduce the feature that allow a transport to use its body as fire position.

Possible Implementation:

[SOMEVEHICLE]
OpenTopped.BodyShot=no   ; boolean, if yes, passengers' FLH will be based on body rather than turret