Support EFFECT_ADJUST_VALID_FEATURES_DISTRICTS modifier type.

Fix a bug where aqueduct didn't check mountains that are near rivers.

Fix bug where yields are not cleared after changing to an unsupported type. Allow marking goody hut and barbarian camp as a city center, by prefixing the tack name with "city".

Try to support Linux.

Compatible with the well-known Map Tacks mod.

Don't count districts that belongs to other player when calculating district adjacency bonuses.

1. Fixed bug where UD holy sites are not calculating patheon adjacency bonuses like sacred path.
2. Indicate if the map tack represented district or wonder can be placed at the given position.
3. Allow double clicking map tack icon in the selection popup to confirm tack placement.

Fix settings screen language.

Add ability to delete map tacks through hotkeys.

Enable adding map tacks and show/hide all map tacks through Hotkeys.