[Bleeding] Added Conversations API. Addresses BUKKIT-864

By: rmichela <deltahat@gmail.com>

paper-api/src/main/java/org/bukkit/conversations/MessagePrompt.java

@@ -0,0 +1,37 @@
+package org.bukkit.conversations;
+
+/**
+ * MessagePrompt is the base class for any prompt that only displays a message to the user and requires no input.
+ */
+public abstract class MessagePrompt implements Prompt{
+
+    public MessagePrompt() {
+        super();
+    }
+
+    /**
+     * Message prompts never wait for user input before continuing.
+     * @param context Context information about the conversation.
+     * @return
+     */
+    public boolean blocksForInput(ConversationContext context) {
+        return false;
+    }
+
+    /**
+     * Accepts and ignores any user input, returning the next prompt in the prompt graph instead.
+     * @param context Context information about the conversation.
+     * @param input Ignored.
+     * @return The next prompt in the prompt graph.
+     */
+    public Prompt acceptInput(ConversationContext context, String input) {
+        return getNextPrompt(context);
+    }
+
+    /**
+     * Override this method to return the next prompt in the prompt graph.
+     * @param context Context information about the conversation.
+     * @return The next prompt in the prompt graph.
+     */
+    protected abstract Prompt getNextPrompt(ConversationContext context);
+}