Change squadrons to operate out of a single base.

https://github.com/dcs-liberation/dcs_liberation/issues/1145

Currently this is fixed at the start of the campaign. The squadron
locations are defined by the campaign file.

Follow up work:

* Track aircraft ownership per-squadron rather than per-airbase.
* UI for relocating squadrons.
* Ferry missions for squadrons that are relocating.
* Auto-relocation (probably only for retreat handling).

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1138

qt_ui/windows/AirWingDialog.py

@@ -34,13 +34,17 @@ class SquadronDelegate(TwoColumnRowDelegate):
         return index.data(AirWingModel.SquadronRole)
 
     def text_for(self, index: QModelIndex, row: int, column: int) -> str:
+        squadron = self.squadron(index)
         if (row, column) == (0, 0):
-            return self.squadron(index).name
+            if squadron.nickname:
+                nickname = f' "{squadron.nickname}"'
+            else:
+                nickname = ""
+            return f"{squadron.name}{nickname}"
         elif (row, column) == (0, 1):
-            squadron = self.air_wing_model.data(index, AirWingModel.SquadronRole)
             return squadron.aircraft.name
         elif (row, column) == (1, 0):
-            return self.squadron(index).nickname or ""
+            return squadron.location.name
         elif (row, column) == (1, 1):
             squadron = self.squadron(index)
             active = len(squadron.active_pilots)