New convoy mission

Hi,

I have created a convoy mission. It was quite time consuming to get it work smoothly.
I did a lot of testing. I hope it gets into the next release. :-)

Mission description
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3 Hunters (one with MG and one with grenade launcher) with 12 soldiers (inside the Hunters) start in the north of Stratis. They try to get to the south of the map. The players have to stop the convoy and kill all soldiers. They then get rewarded with an ammobox with some good weapons and as a bonus if they manage to not destroy the vehicles of the convoy, they additionally get the Hunters.

It's quite hard to solo this mission. A team of 3 to 5 players is recommted. I can imagine that the mission is even more fun when you have to fight the other player teams additionally.

Some technical details
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- The convoy mainly drive on the road. Only if they get attacked they may get off road for a short time (while they get attacked).
- Sometimes the cars get stucked on objects that spawned on the the road. But that is not so fatal.