Added comments controller, model, repo, and the database schema. Modified existing Page model to associate with comments.

app/Repos/CommentRepo.php

@@ -0,0 +1,17 @@
+<?php namespace BookStack\Repos;
+
+use BookStack\Comment;
+use BookStack\Entity;
+
+/**
+ * Class TagRepo
+ * @package BookStack\Repos
+ */
+class CommentRepo {
+    /**
+     *
+     * @var Comment $comment 
+     */
+    protected $comment;
+    
+}