Added MaxSpeed methods to minecards. Added MaxSpeed methods to boats. Added SlowWhenEmpty, FlyingMod, and DerailedMod methods to minecarts.

Signed-off-by: afforess <afforess@gmail.com>

By: afforess <afforess@gmail.com>

paper-api/src/main/java/org/bukkit/entity/Boat.java

@@ -6,4 +6,17 @@ package org.bukkit.entity;
  * @author sk89q
  */
 public interface Boat extends Vehicle {
+    /**
+     * Gets the maximum speed of a boat. The speed is unrelated to the velocity.
+     *
+     * @param speed
+     */
+    public double getMaxSpeed();
+
+    /**
+     * Sets the maximum speed of a boat. Must be nonnegative. Default is 0.4D.
+     *
+     * @param speed
+     */
+    public void setMaxSpeed(double speed);
 }