Bunker Structures

Added 5x Bunker Houses to the player structures that Structure Traders can craft.
Each bunker will take up 4 Lots and cost 35 credits per hour in maintenance fees.
Bunkers have a base item limit of 2,000.
Bunkers will take about the same amount of resources as a Large House.
Each bunker has a unique interior design. Only one of the bunkers (Bunker 4) has a different exterior design as well, otherwise they all have the grey block exterior look.
Player Bunkers now have the correct maintenance of 30 credits / hour.
Player Bunkers now have their signs showing (only default sign is available).
Player Bunkers are now considered guild halls so you can withdraw maintenance and use them as a guild hall.