Balance tweaks, deep sea art, lots of fixes

v1.0.3.6
- First pass deep sea art added to maps, polish/fixes to follow.
- Increased wealth amounts required to complete Hanging Gardens wonder.
- Slightly increased population amounts required to complete Pyramids wonder.
- Added and removed some opportunities from the list of backups for better late game opportunity choices.
- You can no longer pay for a unit and not get it, if you put it in an invalid terrain type.
- Clicking on a fleet when moving an army or vice versa will no longer highlight the wrong set of possible destination tiles.
- Fixed some usernames appearing incorrectly in some languages.
- Fixed erroneous difficulty tooltip on wealth panel during multiplayer.
- Fixed rare issue with Battering Ram and Triremes not triggering correctly.
- Fixed Epic March and Odyssean Voyage not triggering if you spent exactly the target food amount.
- Fixed an incorrect terrain tile near Harappans on Asia.
- Removed redundant AI log keyboard shortcut from Settings.
- Minor text and localisation improvements.
- Players should be more consistently shown as online in multiplayer via the yellow icon on their empire portrait.
- Fixed a bug where the player with least treasure wouldn't get priority when picking empires.
- Added more checks to ensure players are playing on the correct game version in multiplayer.
The final 3 changes will arrive with a server update in ~7 hours so there will be a short outage then. For people with long-running async games, there is a new branch in Steam `v1.0.2.x-multiplayer-compatibility`, which lets you play on the previous game version, so you can finish these games.