Add Jump Nodes

[Goosius1]

• A jump node is part of the wider travel scheme
• A jump node is a new plot type, with configurable cost and upkeep
• 2 towns can build a Fast-Travel route between them
• First town A puts a sign like this at its jump node.

  >>>
  Fast Travel To
    B

• Then Town B puts a sign like this at its jump node:

   >>>
  Fast Travel To
   A

• Now anyone can fast travel the route, simply by right-clicking on either sign.