Add remove asset(s) button to Bynder plugin

A customer has a pull request here https://github.com/bloomreach/ui-extensions/pull/10 to add a remove asset button to replace clicking on the image to remove behavior. 

However, the customer's request does not work for multiple assets. There for we will add support for multiple assets to remove asset button. 

Orion has access to the code https://github.com/bloomreach/ui-extensions