MongoDB support

I tested this module in Drupal installation which uses mongo field storage.
It seems that the module doesn't work properly, since the code has one SQL specific EFQ:
$query->propertyCondition($label_column, '%' . $last_label . '%', 'LIKE');
If I changed this to:
$query->propertyCondition($label_column, $last_label, 'CONTAINS');
Then the module works.