BlockState for Command Blocks. Adds BUKKIT-3805.

By: Nate Mortensen <nate.richard.mortensen@gmail.com>

paper-api/src/main/java/org/bukkit/block/CommandBlock.java

@@ -0,0 +1,40 @@
+package org.bukkit.block;
+
+public interface CommandBlock extends BlockState {
+
+    /**
+     * Gets the command that this CommandBlock will run when powered.
+     * This will never return null.  If the CommandBlock does not have a
+     * command, an empty String will be returned instead.
+     *
+     * @return Command that this CommandBlock will run when powered.
+     */
+    public String getCommand();
+
+    /**
+     * Sets the command that this CommandBlock will run when powered.
+     * Setting the command to null is the same as setting it to an empty
+     * String.
+     *
+     * @param command Command that this CommandBlock will run when powered.
+     */
+    public void setCommand(String command);
+
+    /**
+     * Gets the name of this CommandBlock.  The name is used with commands
+     * that this CommandBlock executes.  This name will never be null, and
+     * by default is "@".
+     *
+     * @return Name of this CommandBlock.
+     */
+    public String getName();
+
+    /**
+     * Sets the name of this CommandBlock.  The name is used with commands
+     * that this CommandBlock executes.  Setting the name to null is the
+     * same as setting it to "@".
+     *
+     * @param name New name for this CommandBlock.
+     */
+    public void setName(String name);
+}