PROPOSED ruleset settings for the M3 game

[Corbeau]

For now, the #poll on Discord is going overwhelmingly in favour of:

- restrictinfra ON
- no classic (diplomatic) tech trade

Further suggestions I believe would improve the game are:
- workers gain experience as they work (LT standard)
- city gets +1 shield on any terrain it is built on (in MP default this happens only on Grassland)
- techleak ON