new attribute aerial_movement_multiplier

Solely for the purpose of creating custom content in servers or maps, implement a new attribute which allows modifying an entity's influence on its aerial velocity.

If set to 0, the entity can still move midair but will not be able to influence its trajectory. Like for players will not be able to turn mid-air after a grounded moving jump.

I think this will go well with the new air drag, friction and bounciness attributes for map making and servers!!