Bug 890647 - [email] unfork value_selector.css

We still have a value_selector.js because the shared one is really just CSS and images, and we just need to generate HTML that matches that CSS like the shared/style/value_selector/index.html does.

Went to using tmpl resources instead of inlined HTML to avoid the HTML-in-JS escaping thing.

Removed images that are no longer needed. mail_common.js had a dynamic require([]) that asked for value_selector, but mail_common as a module already asked for it, so just removed from the require since it was not doing anything useful.

The override selectors in common.css are long because the ones in the shared value_selector was just as long, and we want to override to get the folder indenting we prefer.

Goofy link comment in the index.html since other build changes broke the gaia_share.json mechanism.