IFA3 Compatibility

What's been done:

- [x] AGM_GForceCoef for German and Russian pilots.

- [x] Bipod support for weapons with a bipod.

- [x] Barrel swapping for weapons that can swap a barrel.

- [x] Disabled AGM FCS for armor. IF/IFA3 has it's own manual FCS for vehicles.

- [x] Generic backblast values for AT launchers.

- [x] Generic overheating values for German, Russian and American small arms.

- [x] Generic overpressure values for German and Russian tank cannons.

- [x] The Panzerfaust has been made to use the AGM disposable weapon system.


What's not done:

- [ ] AGM_BulletMass for ammo types.

- [ ] AGM_GForceCoef for American pilots.

- [ ] Generic overpressure values for American tank cannons.

- [ ] Overpressure values for German or Russian howitzers.

- [ ] Accurate values everywhere.

I mentioned it in the issue [where I was asked if I would contribute what I had](https://github.com/KoffeinFlummi/AGM_Compatibility/issues/2#issuecomment-66181210) but [someone else has done some work for compatibility](http://dev.withsix.com/projects/ironfront-build/repository/revisions/a7fadea9febfc90aeb5e7e75120be53284592f74) as well on the IF tracker on Dev-Heaven.

From the list above, there's still some things left to do. There could be more that needs to get done as well?  I can do the rest of what's listed but it'll be a bit before I get to it. The group I help run has our anniversary coming up which means I have some mission making to get done. It'll be mid January-ish before I can pick this up again.