Cannon foundry dummy

Voted to drop the complex bronze (tin + copper + ...) lines now. Iron.
Might want to combine this with weaponsmith, as they are similar.
Convince resource overview bar to not crash (for now)
Fix some tier categories in new dummy building constants
Add dummy buildings to per-tier build menu (as comments)

The headlines can go live already, nobody is going to see any of this in
real games anyways due to TIER.CURRENT_MAX.
Fix cannon foundry building id

This might actually exist soon, yay!
Add cannon foundry build menu icons, enable in per-tier build menu
Fix typo