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

resources/doctrines/coldwar.yaml

@@ -0,0 +1,32 @@
+name: coldwar
+cap: true
+cas: true
+sead: true
+strike: true
+antiship: true
+rendezvous_altitude_ft_msl: 22000
+hold_distance_nm: 15
+push_distance_nm: 10
+join_distance_nm: 10
+max_ingress_distance_nm: 30
+min_ingress_distance_nm: 10
+ingress_altitude_ft_msl: 18000
+min_patrol_altitude_ft_msl: 10000
+max_patrol_altitude_ft_msl: 24000
+pattern_altitude_ft_msl: 5000
+cap_duration_minutes: 30
+cap_min_track_length_nm: 12
+cap_max_track_length_nm: 24
+cap_min_distance_from_cp_nm: 8
+cap_max_distance_from_cp_nm: 25
+cap_engagement_range_nm: 35
+cas_duration_minutes: 30
+sweep_distance_nm: 40
+ground_unit_procurement_ratios:
+    Tank: 4
+    ATGM: 2
+    APC: 3
+    IFV: 2
+    Artillery: 1
+    SHORAD: 2
+    Recon: 1

resources/doctrines/modern.yaml

@@ -0,0 +1,32 @@
+name: modern
+cap: true
+cas: true
+sead: true
+strike: true
+antiship: true
+rendezvous_altitude_ft_msl: 25000
+hold_distance_nm: 25
+push_distance_nm: 20
+join_distance_nm: 20
+max_ingress_distance_nm: 45
+min_ingress_distance_nm: 10
+ingress_altitude_ft_msl: 20000
+min_patrol_altitude_ft_msl: 15000
+max_patrol_altitude_ft_msl: 33000
+pattern_altitude_ft_msl: 5000
+cap_duration_minutes: 30
+cap_min_track_length_nm: 15
+cap_max_track_length_nm: 40
+cap_min_distance_from_cp_nm: 10
+cap_max_distance_from_cp_nm: 40
+cap_engagement_range_nm: 50
+cas_duration_minutes: 30
+sweep_distance_nm: 60
+ground_unit_procurement_ratios:    
+    Tank: 3
+    ATGM: 2
+    APC: 2
+    IFV: 3
+    Artillery: 1
+    SHORAD: 2
+    Recon: 1

resources/doctrines/ww2.yaml

@@ -0,0 +1,31 @@
+name: ww2
+cap: true
+cas: true
+sead: false
+strike: true
+antiship: true
+hold_distance_nm: 10
+push_distance_nm: 5
+join_distance_nm: 5
+rendezvous_altitude_ft_msl: 10000
+max_ingress_distance_nm: 7
+min_ingress_distance_nm: 5
+ingress_altitude_ft_msl: 8000
+min_patrol_altitude_ft_msl: 4000
+max_patrol_altitude_ft_msl: 15000
+pattern_altitude_ft_msl: 5000
+cap_duration_minutes: 30
+cap_min_track_length_nm: 8
+cap_max_track_length_nm: 18
+cap_min_distance_from_cp_nm: 0
+cap_max_distance_from_cp_nm: 5
+cap_engagement_range_nm: 20
+cas_duration_minutes: 30
+sweep_distance_nm: 10
+ground_unit_procurement_ratios:
+    Tank: 3
+    ATGM: 3
+    APC: 3
+    Artillery: 1
+    SHORAD: 3
+    Recon: 1