Add bunker AI build plans to newly added scenes

[MyNameIsTrez]

Is your feature request related to a problem? Please describe.
Sites new to pre3 won't have bunkers automatically built for them when the player allocates gold for them.

This can lead situations where the player may think he has spent enough gold for a bunker to be built automatically for him, but when the player is attacked they'll realize that no bunker has been built, meaning almost certain death for the player. It's also not obvious to the player which sites are the newly added pre3 ones and which aren't, so this disincentivizes players from using the Auto-build option until this issue has been resolved.

[garethyr]

My plan for this is to source builds from people who wanna contribute them after pre4 is out. There are a lot of new maps and adding prebuilt bunkers for Bunker Breach/Siege and Metagame step-by-step bunkers to them would be great.

Good to have the issue though, as a reminder, so thanks.