* Removed PilzAdam's carts
* Replaced by SmallJoker's Boost_cart
(https://github.com/SmallJoker/boost_cart)
* Modified to fully replace carts
* Modified for MFF :
- desactivate mesecons
- power_rail: accelerate, max_speed set in init.lua
- brake_rail: deccelerate, min_speed set in init.lua (so the cart
doesn't stop and runs at very low speed)
- default:rail / rail_cooper : no friction, keep the current speed
- no collision (avoid the "walled_in" bug)
