Properly escape Context UI block ID's

Certain module create exotic block ID's like search_api@flatstore:block:size

ID's containing the "@" sign pose a problem for jQuery selectors. It is required to use cleanup function like drupal_html_id() or drupal_html_css() before outputting block ID's as CSS ID's or classes.

The problem with Context UI is that I cannot add/remove/move such blocks (jQuery breaks).

For reference, see this issue #1284156: Block deltas contain characters that aren't correctly filtered as CSS identifiers on block administration pages for Facet API., Originally (I thought it was their issue, but apparently it is a COntext UI problem.