Add 'Strip CSS/JS query strings' to dev. tools

stylz.css?blarg71 -> stylz.css

The cachebuster query strings break in-browser development and mean I have to hunt for my js file every time Drupal clears the CSS/JS cache.

Really, I would rather this were in core so I could $conf['css_js_query_strings'] = FALSE; and then never think about it again but there is not a lot of movement on the issue there → and that patch is harder to write and I don't want to have to figure out how to do this in D8.