Fix UI to obey max group sizes.

This also adds max group sizes for aircraft that need it but don't
according to DCS. Only the first tanker or AEW&C unit in a group can be
contacted by radio.

resources/units/aircraft/A-50.yaml

@@ -1,4 +1,5 @@
 description: The A-50 is an AWACS plane.
+max_group_size: 1
 price: 50
 variants:
   A-50: null

resources/units/aircraft/E-2C.yaml

@@ -1,5 +1,7 @@
 carrier_capable: true
-description: The Northrop Grumman E-2 Hawkeye is an American all-weather, carrier-capable
+max_group_size: 1
+description:
+  The Northrop Grumman E-2 Hawkeye is an American all-weather, carrier-capable
   tactical airborne early warning (AEW) aircraft.
 introduced: 1973
 manufacturer: Northrop Grumman

resources/units/aircraft/E-3A.yaml

@@ -1,4 +1,5 @@
 description: The E-3A is a AWACS aicraft.
 price: 50
+max_group_size: 1
 variants:
   E-3A: null

resources/units/aircraft/IL-78M.yaml

@@ -1,3 +1,4 @@
 price: 20
+max_group_size: 1
 variants:
   IL-78M: null

resources/units/aircraft/KC-135.yaml

@@ -1,6 +1,9 @@
-description: The Boeing KC-135 Stratotanker is a military aerial refueling aircraft
-  that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner.
+description:
+  The Boeing KC-135 Stratotanker is a military aerial refueling aircraft that
+  was developed from the Boeing 367-80 prototype, alongside the Boeing 707
+  airliner.
 introduced: 1957
+max_group_size: 1
 manufacturer: Beoing
 origin: USA
 price: 25

resources/units/aircraft/S-3B.yaml

@@ -1,5 +1,6 @@
 carrier_capable: true
-description: The Lockheed S-3 Viking is a 4-crew, twin-engine turbofan-powered jet
+description:
+  The Lockheed S-3 Viking is a 4-crew, twin-engine turbofan-powered jet
   aircraft that was used by the U.S. Navy (USN) primarily for anti-submarine warfare.
   In the late 1990s, the S-3B's mission focus shifted to surface warfare and aerial
   refueling. The Viking also provided electronic warfare and surface surveillance
@@ -14,6 +15,7 @@ introduced: 1984
 manufacturer: Lockheed
 origin: USA
 price: 10
+max_group_size: 1
 role: Carrier-based Attack
 variants:
   S-3B Viking: {}