Minor fixes to statement, services and internal things

Many misc updates

modules/service/classes/model/service.php

@@ -12,6 +12,9 @@
  */
 class Model_Service extends ORMOSB {
 	// Relationships
+	protected $_has_one = array(
+		'service_billing'=>array('far_key'=>'account_billing_id','foreign_key'=>'id'),
+	);
 	protected $_has_many = array(
 		'invoice'=>array('through'=>'invoice_item'),
 	);
@@ -108,14 +111,6 @@ class Model_Service extends ORMOSB {
 			return $plugin->_admin_update();
 	}
 
-	// @todo To implement
-	/**
-	 * Calculate the tax for this item
-	 */
-	public function tax() {
-		return $this->price * .1;
-	}
-
 	/** LIST FUNCTIONS **/
 
 	public function list_active() {