Make save names clearer

[ChrisNeedham24]

• As great as a timestamp is for a save name, it would be preferable for them to include other distinguishing details.
• Ideally, the new format would include the faction and turn in addition to the timestamp.
• For multiplayer games, the game name should be included as well - though consideration would also be required then for whether loading a game with an old game name still tries to use that game name. What happens if another lobby is using it, for example? Either way, it would potentially help players.
• Could we change the timestamp to be epoch seconds and then just parse that as an ISO timestamp? Could shorten the overall length.

[ChrisNeedham24]

Just had a thought that the actual save file name should be effectively minified - like we can use epoch seconds plus a faction abbreviation and turn, maybe a lobby name abbreviation for multiplayer games too. We would then display the full name in-game.

[ChrisNeedham24]

Another thought is that now post #173 we'll want to differentiate single and multiplayer games so that saves from LAN games hosted on a local machine don't appear under single player.