Doctrine load from YAML (#3291)

This PR refactors the Doctrine class to load from YAML files in the
resources folder instead of being hardcoded as a step towards making
doctrines moddable (Issue #829).

I haven't added anything to the changelog as a couple of things should
get cleaned up first:
- As far as I can tell, the flags in the Doctrine class (cap, cas, sead
etc.) aren't used anywhere. Need to test further, and if they're truly
not used, will remove them.
- Probably need to update the Wiki

game/flightplan/waypointsolverloader.py

@@ -11,17 +11,14 @@ from shapely import transform
 from shapely.geometry import shape
 from shapely.geometry.base import BaseGeometry
 
-from game.data.doctrine import Doctrine, ALL_DOCTRINES
+from game.data.doctrine import Doctrine
 from .ipsolver import IpSolver
 from .waypointsolver import WaypointSolver
 from ..theater.theaterloader import TERRAINS_BY_NAME
 
 
 def doctrine_from_name(name: str) -> Doctrine:
-    for doctrine in ALL_DOCTRINES:
-        if doctrine.name == name:
-            return doctrine
-    raise KeyError
+    return Doctrine.named(name)
 
 
 def geometry_ll_to_xy(geometry: BaseGeometry, terrain: Terrain) -> BaseGeometry: