Asset deletion improvements

When the user deletes assets, we should 

Allow Shift select to select multiple on the list

How it should work:

• The user selects one item from the top of the list
• Holds down the SHIFT key and select one from below. 
• All items between the first and last selected would be selected

Confirmation of deleting items

Should not have the possibility to not show the confirmation again. This reduces the error prevention a lot.

Remove the checkbox from view.