Blocks 2.4.18

Moving blocks_core.css styles into blocks_style.css stylesheet; removing blocks_core.css
Minifying main stylesheets
Passed non-conditional thumbnail size to Popout Post template
Removed conditional popout-thumb thumbnail size; was rendering re-scaled full-size thumbnails
Minifying Popout Post JS and CSS
Loading Popout Post JS in head, but with defer
Loading Popout Post CSS asynchronously
Minor CSS fixes