rename with execution order, add desc & initial creation script

tools/migration/shell.1489951459.like-to-reactions.js

@@ -0,0 +1,22 @@
+db.users.update({}, {
+	$unset: {
+		likes_count: 1,
+		liked_count: 1
+	}
+}, false, true)
+
+db.likes.renameCollection('post_reactions')
+
+db.post_reactions.update({}, {
+	$set: {
+		reaction: 'like'
+	}
+}, false, true)
+
+db.posts.update({}, {
+	$rename: {
+		likes_count: 'reaction_counts.like'
+	}
+}, false, true);
+
+db.notifications.remove({})