Add WorldGuard integration support

[Rumsfield]

Add support for WorldGuard: Add custom flags and session handlers.

• [x] Claiming land (includes settle, camp & kingdom create)
• [x] Unclaiming land from towns
• [x] Travel entry
• [x] Travel exit

[Rumsfield]

• Changed new town init water checks to only be within depth limit, not whole chunk.
• Fixed internal errors in admin unclaim command.