Add construction of road barricade

For people who want to slow down animals or block off streets to theoretical NPC drivers without having to go near roadblock turrets or chicken walkers. Could be worth increasing their movement cost for more utility.

(Please ignore commits pertaining to merging from mainline; I still haven't quite figured out how to update my fork's master on the website version of GitHub otherwise.)
These double-brackets threw off the parser.  I've fixed it as part of merging, but keep in mind for the next time, please.