Improve union shape rhombus.
Refactor various methods.
Fix union shape triangle.
Reset other items in EditSettlementDialog when owner changes.
"save and quit" action is racey in MapEditor, replace with just quit.
Fix remaining native settlement edit issues, BR#2676
Minor cleanup.
Fix failure in Ability deletion.
Add delete attribute handling for <production>.
Compatibility clarification.
Classic horses eat fish, freecol horses eat grain.
Fix "Start Game" in map editor, BR#2129.