Add more varieties of Dustbowl in the Dustbowl Class Wars servers

[Sarsath]

These include:

• Destructible Dustbowl (cp_dustbowl_destructible) https://steamcommunity.com/sharedfiles/filedetails/?id=2960473995
• Dustbowl Improved https://steamcommunity.com/sharedfiles/filedetails/?id=2636112118
• Payload Dustbowl (pl_dustbowl) https://steamcommunity.com/sharedfiles/filedetails/?id=2417002105
• The Expanded Dustbowl https://steamcommunity.com/sharedfiles/filedetails/?id=2461676175
• Dustbowl 2007 https://steamcommunity.com/sharedfiles/filedetails/?id=2711007892