Feature: Modular airports

[J0anJosep]

Description

This PR changes old state machines for airports and aircraft. Old airports are converted into new customizable airports. It also adds rotated airports by default and two small airport layouts for testing. Default layouts can still be built as before.

Modular airports are enabled with the "Allow customized airports" setting.

OpenGFX+Airports and other Airport related NewGRFs are supported now.

To compile and test it with the appropriate sprites a specific version of grfcodec is needed: https://github.com/J0anJosep/grfcodec

To-Do list

Fix small movement offsets.
Start working with NewGRF:

• Provide airtype graphics
• Provide airport layouts

Long term To-Check/To-Revise list

1. IMPORTANT: Aircraft controller. Check it works in all cases.
2. CHECK: Aircraft entry points and on hold flight.
3. CHECK: Aircraft flight level.
4. CHECK: Aircraft speed.
5. CHECK: On closed airports, keep aircraft on hold. Also for helicopters.
6. TEST: zeppelin disaster
7. TEST: regression tests, ia, scripts... (test)
8. TEST: build airport commands: AT_CUSTOM, noise, costs and maintenance costs...
9. LOW PRIORITY: License of sprites: Got them from OpenGFX+ Airports. Check how to mention this and license. Occasionally, get adequate sprites.
10. LOW PRIORITY: Sprites: remove (or reorder) unused. Use AirportTypeInfo for getting sprites to draw. And use overrides from newgrf. At some point, maybe use airportspecs.
11. LOW PRIORITY: Check savegames using airportsplus and other airport NewGRFs are converted correctly.
12. LOW PRIORITY: What to do with savegames containing unknown airport designs.
13. LOW PRIORITY: Decide whether Airport TileArea should be a BitmapTileArea (it will ease dealing with airport noise).
14. LOW PRIORITY: Rewrite functions involving airport noise and simplify them.
15. LOW PRIORITY: Revise oil rigs.
16. LOW PRIORITY: Add support for newgrf airtypes, airporttiles and airport layouts.