[Bleeding] Added Conversations API. Addresses BUKKIT-864

By: rmichela <deltahat@gmail.com>

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

@@ -0,0 +1,19 @@
+package org.bukkit.conversations;
+
+import org.bukkit.command.CommandSender;
+
+/**
+ * NullConversationPrefix is a {@link ConversationPrefix} implementation that displays nothing in front of
+ * conversation output.
+ */
+public class NullConversationPrefix implements ConversationPrefix{
+
+    /**
+     * Prepends each conversation message with an empty string.
+     * @param context Context information about the conversation.
+     * @return An empty string.
+     */
+    public String getPrefix(ConversationContext context) {
+        return "";
+    }
+}