[Suggestion] Docking station

[jglrxavpok]

See #36

From wormzjl on Reddit:

If you use a dock, the boat itself can be a pure visual effect instead of a in-world entity while docked. This would make things looked better and is more friendly for performace.

This will also make automation easier, since one can refer to the dock directly instead of inputting the coordinate when making paths (looking at the suggestion about mapping table above).