Add BlockLabel and BlockID as data attribute for DetailView

You add the Block Identifier as class within HTML.
This makes it impossible for custom blocks to select them by jQuery.
Class attribute then looks like class="block block_custom block" if headline is "custom block".

I add data-block="blockkey" and data-blockid="blockid" in DetailView and only data-block="blockkey" to EditView.
Maybe you also have a way to add blockid within EditView. But I don't see an easy one.

To give Extensions the chance to safely select blocks in HTML.