Make error message boxes closable

@atul ghate

I have applied your patch, it work fine on:
+ Display close button.
+ Close message when click.
But, I see a close button already exists on the claro theme. I think the styling should be identical.
Otherwise, a light box shadow seems not Claro style.
Here is a close button on views popup:

My two cents

I change status to needs work

@atul_ghate thanks for the work you did, I took @tra.duong's suggestion and implemented the dialog button's html and styles for the message. Sharing in case anyone else wants the patch, I doubt it'll make it into core but I like being able to close the messages.