New equipment

As it seems everyone is putting their new-* branches out there for the world to see, I thought I'd do the same.

This is work in progress. I have a working implementation on the Lua side of things, but the C++ is still very unaware of it and considers that you fly on bare metal most of the time. Also, it doesn't get saved yet due to me still having to look at the serialize code.

The API is quite straigthforward : on the Lua side the method names are the same, the argument order should be the same, etc etc... On the C++ side, every bit of information that is not UI related should be obtained via GetModifier calls. I've also built an infrastructure for random junk in case integers don't suffice, but the more I progress the more I think that if I need it I'm doing something wrong.

Critics are welcome, patches even more :-)
`fuel_max` is never defined before this point, right? So I don't see the point in the `or` statement.