Add search option for issue #2104
fixes #2138
Don't return incorrect artist finder results

Applies to nicoseiga, tumblr, and deviantart; fixes #2134
Automatically focus first autocomplete result

In order to do this space-to-complete needs to be removed too since it
doesn't work together with autofocus. I think this is a good thing
anyway as it can cause accidental selections when typing. And we already
have two other shortcuts for this too (enter and tab).
Upload preview: use normalized image url

This means that the preview will work even when the user doesn't use the
direct image link. e.g. The user can use the bookmarklet on Pixiv
mode=medium pages.