Add some developer doc for check_account_password hook

doc/hook/check_account_password.bb

@@ -1 +1,17 @@
 [h2]check_account_password[/h2]
+Use this hook to provide additional checks or validations of the password given when
+registering and account.
+[h3]Arguments:[/h3]
+[code=php]array(
+	'password' => $password,	// The password to check
+	'result' => array(
+		'error' => false,
+		'message' => ''
+	)
+)[/code]
+[h3]Results:[/h3]
+For a failed check set the [code]error[/code] member of the [code]result[/code]
+array to [code]true[/code] and the [code]message[/code] to a short message
+explaining why it failed.
+
+Otherwise, leave it alone.