[Bleeding] Added Conversations API. Addresses BUKKIT-864

By: rmichela <deltahat@gmail.com>

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

@@ -0,0 +1,16 @@
+package org.bukkit.conversations;
+
+/**
+ * StringPrompt is the base class for any prompt that accepts an arbitrary string from the user.
+ */
+public abstract class StringPrompt implements Prompt{
+
+    /**
+     * Ensures that the prompt waits for the user to provide input.
+     * @param context Context information about the conversation.
+     * @return True.
+     */
+    public boolean blocksForInput(ConversationContext context) {
+        return true;
+    }
+}