[Bleeding] Added Conversations API. Addresses BUKKIT-864

By: rmichela <deltahat@gmail.com>

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

@@ -0,0 +1,17 @@
+package org.bukkit.conversations;
+
+import org.bukkit.command.CommandSender;
+
+/**
+ * A ConversationPrefix implementation prepends all output from the conversation to the player.
+ * The ConversationPrefix can be used to display the plugin name or conversation status as the conversation evolves.
+ */
+public interface ConversationPrefix {
+
+    /**
+     * Gets the prefix to use before each message to the player.
+     * @param context Context information about the conversation.
+     * @return The prefix text.
+     */
+    String getPrefix(ConversationContext context);
+}