FlightGear - Flight Simulator FGAddon

* Numerous bugfixes to fuel predictions and FMGC
* Addition of simbrief API integration - ability to pull flightplan loaded in simbrief
* Addition of NOAA API integration - ability to pull weather in MCDU
* Bugfixes to electrical system in battery-only state
* Bugfixes to fuel LP valves so that fire extinguishers will shutdown engines
* Bugfixes to managed speed (cost index 0 now works)
* Improvement to vertical speed needle (amber warning at low altitude)
* Addition of shutdown sound (with GNU GPL 2.0 permission from Adam Murphy of Sky High Sounds)
* Correction of dimming of MCDU
* Correction of right MCDU power source