(UI) Politics overview diagram: Add legend popup (#10451)

* Refactor Battle damage shadowed Label into reusable WidgetGroup

* Make Politics Overview "Grid header" fixed and some linting

* Add a Legend popup explaining line colors in the Politics Overview Diagram: Click inside

* Missing translation template

* Final decision on background didn't make it in properly

* Remove unused png - those are now in the Construction atlas

* Smaller background image

* Color and shadow choices

* Redo atlas to include both 10505 and this

android/Images/OtherIcons/Politics-diagram-bg.readme.txt

@@ -0,0 +1,7 @@
+Used in GlobalPoliticsOverviewTable.DiagramLegendPopup as "easter egg" background.
+
+Uses 256x256 pixels in its atlas - at the time of adding it, there was ample leftover room,
+but once the main atlas fill up, please move to another or even its own little atlas,
+and maybe drop this file.
+
+Will be seldom used!

android/assets/jsons/translations/template.properties

@@ -1424,6 +1424,7 @@ Number of your cities\ndemanding this resource for\n'We Love The King Day' =
 Politics = 
 Show global politics = 
 Show diagram = 
+Diagram line colors = 
 At war with [enemy] = 
 Defensive pact with [civName] = 
 Friends with [civName] =