Add 'unknown' and 'challange' to target.type enum.

We'll delete these targets later, but for now I want to be able to
insert them.

comments/database.sql

@@ -21,7 +21,7 @@ CREATE TABLE users (
 CREATE TABLE targets (
     id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
     domain VARCHAR(255) NOT NULL, -- combines sdk & version
-    type ENUM('class', 'guide', 'video') NOT NULL DEFAULT 'class',
+    type ENUM('class', 'guide', 'video', 'unknown', 'challenge') NOT NULL DEFAULT 'class',
     cls VARCHAR(255) NOT NULL,    -- "Ext.draw.Sprite"
     member VARCHAR(255) NOT NULL  -- "method-setAttributes"
 );