Add Transform Action for mods (#8120)

* Initial version of code

* Enable cost=0 for buttons

* Add Conditional to Transform

* Fix translation file

* Add icon
Allow other Conditionals

* Updated icon

* Add credit

* switch hotkey

* Fix icon

* Remove Conditional Costs

* Remove vestigal Stats costs for Transform

* Minor cleanup

android/assets/jsons/translations/template.properties

@@ -946,6 +946,8 @@ Add in capital =
 Add to [comment] = 
 Upgrade to [unitType] ([goldCost] gold) = 
 Upgrade to [unitType]\n([goldCost] gold, [resources]) = 
+Transform to [unitType] = 
+Transform to [unitType]\n([resources]) = 
 Found city = 
 Promote = 
 Health = 
@@ -1330,6 +1332,7 @@ Can upgrade from [unit] =
 Can upgrade from: = 
 Upgrades to [upgradedUnit] = 
 Obsolete with [obsoleteTech] = 
+Can Transform to [upgradedUnit] = 
 Occurs on [listOfTerrains] = 
 Occurs on: = 
 Placed on [terrainType] =