Change styles and behaviour of Unit flags as in Civ 5 (#8128)

* Change styles and behaviour of Unit flags as in Civ 5

* Make shadow mask an optional (removed from default atlas)

* Make shadow mask an optional (removed from default atlas)

* Remove magical numbers, scaling dependent on a ratio of the source

Co-authored-by: tunerzinc@gmail.com <vfylfhby>

android/assets/game.atlas

@@ -1314,6 +1314,68 @@ UnitActionIcons/Upgrade
   offset: 0, 0
   index: -1
 
+UnitFlags.png
+size: 2048, 1024
+format: RGBA8888
+filter: MipMapLinearLinear, MipMapLinearLinear
+repeat: none
+UnitFlagIcons/UnitFlag
+  rotate: false
+  xy: 0, 0
+  size: 178, 178
+  orig: 178, 178
+  offset: 0, 0
+  index: -1
+UnitFlagIcons/UnitFlagSelection
+  rotate: false
+  xy: 356, 0
+  size: 178, 178
+  orig: 178, 178
+  offset: 0, 0
+  index: -1
+UnitFlagIcons/UnitFlagFortify
+  rotate: false
+  xy: 0, 178
+  size: 178, 178
+  orig: 178, 178
+  offset: 0, 0
+  index: -1
+UnitFlagIcons/UnitFlagSelectionFortify
+  rotate: false
+  xy: 356, 178
+  size: 178, 178
+  orig: 178, 178
+  offset: 0, 0
+  index: -1
+UnitFlagIcons/UnitFlagCivilian
+  rotate: false
+  xy: 0, 356
+  size: 178, 217
+  orig: 178, 217
+  offset: 0, 0
+  index: -1
+UnitFlagIcons/UnitFlagSelectionCivilian
+  rotate: false
+  xy: 366, 385
+  size: 157, 170
+  orig: 157, 170
+  offset: 0, 0
+  index: -1
+UnitFlagIcons/UnitFlagEmbark
+  rotate: false
+  xy: 534, 0
+  size: 178, 210
+  orig: 178, 210
+  offset: 0, 0
+  index: -1
+UnitFlagIcons/UnitFlagSelectionEmbark
+  rotate: false
+  xy: 890, 0
+  size: 178, 210
+  orig: 178, 210
+  offset: 0, 0
+  index: -1
+
 NotificationIcons.png
 size: 512, 64
 format: RGBA8888
@@ -1415,5 +1477,4 @@ NotificationIcons/NextTurn
   xy: 198, 0
   size: 33, 33
   orig: 33, 33
-  offset: 0, 0
-  index: -1
+