Camps: Spawn different enemies based on remaining placer count

[mbeyer]

The idea is to have the mission difficulty scales a bit by mission maker choice. This can be helpful if missions turn out too hard, so reinforcements spawned by camps will be easier.

Example: Spawn T72s if playercount is above 20 once the zone is triggered, otherwise spawn BRDMs.

[simonamdev]

We can set difficulty coefficients such as:
0.8 * Original Player Count = Hard
0.5 * OPC = Medium
0.25 * OPC = Easy
and if certain assets are still alive (example: IFV) and being used the difficulty coefficient decreases (example by -0.1).
Example:

10 guys starting including IFV. when IFV and 3 guys die then the server drops the difficulty to medium (as the amount of people alive is now less than 0.8 * OPC).

10 guys starting including IFV. If only 3 guys die, the server keeps the difficulty at hard as the amount of people alive + the strength of the IFV is still enough to deal with the hard difficulty (despite the amount of people alive being less than 0.8 * OPC, because since the IFV is still alive, the OPC needs to be less than (0.8-0.1) * OPC)