[Bleeding] Added Conversations API. Addresses BUKKIT-864

By: rmichela <deltahat@gmail.com>

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

@@ -0,0 +1,26 @@
+package org.bukkit.conversations;
+
+/**
+ * An ExactMatchConversationCanceller cancels a conversation if the user enters an exact input string
+ */
+public class ExactMatchConversationCanceller implements ConversationCanceller {
+    private String escapeSequence;
+
+    /**
+     * Builds an ExactMatchConversationCanceller.
+     * @param escapeSequence The string that, if entered by the user, will cancel the conversation.
+     */
+    public ExactMatchConversationCanceller(String escapeSequence) {
+        this.escapeSequence = escapeSequence;
+    }
+    
+    public void setConversation(Conversation conversation) {}
+
+    public boolean cancelBasedOnInput(ConversationContext context, String input) {
+        return input.equals(escapeSequence);
+    }
+
+    public ConversationCanceller clone() {
+        return new ExactMatchConversationCanceller(escapeSequence);
+    }
+}