Germany 1944 free unit list fixes.

1. Removes Flak18 as these currently require Kdo.G.40. (part of the WW2
Asset Pack) to fire at player. ED-supplied single missions are having
Flak18s w/out WW2 Asset Pack firing at a point in the air.

2. Adds Opel Blitz to frontline for more variety, balance, and some
little bit of historical accuracy. My understanding is late war was more
truck strafing than HVARing Panzers.

3. Adds guard tower to AAA units to have a functioning AAA since Flak18s
don't work.

resources/factions/germany_1944_free.yaml

@@ -0,0 +1,31 @@
+---
+country: Third Reich
+name: Germany 1944 (Free)
+authors: Khopa
+description: <p>WW2 germany faction that does not require the WW2 asset pack.</p>
+locales:
+  - de_DE
+aircrafts:
+  - "Bf 109 K-4 Kurf\xFCrst"
+  - Fw 190 A-8 Anton
+  - Fw 190 D-9 Dora
+frontline_units:
+  - Truck Opel Blitz
+  - Panzerkampfwagen IV Ausf. H
+  - Sd.Kfz.251 "Hanomag"
+artillery_units: []
+logistics_units:
+  - Truck Opel Blitz
+infantry_units:
+  - Infantry AK-74 Rus
+air_defense_units:
+  - Watch tower armed
+preset_groups: []
+naval_units: []
+requirements: {}
+carrier_names: []
+helicopter_carrier_names: []
+missiles: []
+has_jtac: false
+doctrine: ww2
+building_set: ww2free