Add EWR generation.

Fixes https://github.com/Khopa/dcs_liberation/issues/66

gen/sam/ewrs.py

@@ -0,0 +1,98 @@
+from dcs.vehicles import AirDefence
+from dcs.unittype import VehicleType
+
+from gen.sam.group_generator import GroupGenerator
+
+
+class EwrGenerator(GroupGenerator):
+    @property
+    def unit_type(self) -> VehicleType:
+        raise NotImplementedError
+
+    def generate(self) -> None:
+        self.add_unit(self.unit_type, "EWR", self.position.x, self.position.y,
+                      self.heading)
+
+
+class BoxSpringGenerator(EwrGenerator):
+    """1L13 "Box Spring" EWR."""
+
+    unit_type = AirDefence.EWR_1L13
+
+
+class TallRackGenerator(EwrGenerator):
+    """55G6 "Tall Rack" EWR."""
+
+    unit_type = AirDefence.EWR_55G6
+
+
+class DogEarGenerator(EwrGenerator):
+    """9S80M1 "Dog Ear" EWR.
+
+    This is the SA-8 search radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.CP_9S80M1_Sborka
+
+
+class RolandEwrGenerator(EwrGenerator):
+    """Roland EWR.
+
+    This is the Roland search radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.SAM_Roland_EWR
+
+
+class FlatFaceGenerator(EwrGenerator):
+    """P-19 "Flat Face" EWR.
+
+    This is the SA-3 search radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.SAM_SR_P_19
+
+
+class PatriotEwrGenerator(EwrGenerator):
+    """Patriot EWR.
+
+    This is the Patriot search/track radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.SAM_Patriot_STR_AN_MPQ_53
+
+
+class BigBirdGenerator(EwrGenerator):
+    """64H6E "Big Bird" EWR.
+
+    This is the SA-10 track radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.SAM_SA_10_S_300PS_SR_64H6E
+
+
+class SnowDriftGenerator(EwrGenerator):
+    """9S18M1 "Snow Drift" EWR.
+
+    This is the SA-11 search radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.SAM_SA_11_Buk_SR_9S18M1
+
+
+class StraightFlushGenerator(EwrGenerator):
+    """1S91 "Straight Flush" EWR.
+
+    This is the SA-6 search/track radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.SAM_SA_6_Kub_STR_9S91
+
+
+class HawkEwrGenerator(EwrGenerator):
+    """Hawk EWR.
+
+    This is the Hawk search radar, but used as an early warning radar.
+    """
+
+    unit_type = AirDefence.SAM_Hawk_SR_AN_MPQ_50