FlightGear - Flight Simulator FGAddon

Changes;

* Flight Model
- Improved low speed handling.
- Flaps tuned base on OpenVSP data
- spoiler aero added for yaw, adjusted effectivity at higher alpha based on pilot reports and OpenVSP analysis
- APC now holds alpha rather than airspeed.
- Wingsweep (oversweep) now modelled correctly (JSBSim system rather than Nasal)
- alpha indicated has been aligned based on the touchdown geometry of the hook; optimised for 15degrees indicated.
- new reposition for case 1 inbound
- use of execrate on auxiliary systems to reduce CPU load (a very tiny bit)

* Carrier (with Battle Group) included in Replay
* Air to air refuelling tanker included in Replay
* Improved carrier init; better with 2018.3, but should work with Trumann

* Cockpit / 3d model changes.
- General tidy up of all of the 3d models that make up the cockpit.
- adjusted to use generally material 15 (AC3d)
- Texture fixes
- remove (some 2sided shapes)
- Move all of the external stores into a single 3d model, with a single texture atlas.
- Add animated AOA indexer to nose gear
- Front HSD no longer becomes obscured when moved (due to z-buffering issues)
- reworked all screens to have more consistent colours and CRT fitting into available space.

General
- Added cold and dark.