Don't select images when expanding them

This fixes one of my greatest annoyances with RES, it adds '-X-user-select: none' to expando image icons so you don't accidentally select the image below.

Also, 'user-select' isn't actually recognised in Firefox or Chrome [as explained here](https://developer.mozilla.org/en-US/docs/Web/CSS/user-select "ignore the warning, it's about the fact that it's not in any standards recommendation"), so I removed both instances from res.css.
the theory behind having these present without prefixes is that often it's eventually ratified as a standard and will stop working without the prefixes.

it's fair to say based on that MDN article that that's likely far off in the future for this particular property, so I'm not against removing it, but I don't think we really benefit much from removing it besides having to react someday if/when they do finally recognize it as a standard... I think it might be best to just leave these in since they do no harm.  I'm not taking a hardline stance on it and am open to comments from others though - thoughts anyone?