Add delete modal

To make it easy to remove records in the list page, an extra partial is created:

<?php echo $this->partial('phpro-smartcrud/partial/module-delete'); ?>

This should be set at the bottom of the list. When you click a delete button (.btn-delete) the modal opens.
When you press the '.btn-confirm' button, the record is removed and the page gets reloaded.

One dependency added: rwoverdijk/assetmanager
Only needed when you want to use the partial.