Follow-on from autocomplete updates.

(9345dde83e1f092a9309c45282dc21e3fd408875, d632ef3e50252d388c272cacd29e8cc6e4949cec)
- gallery module: added loading-small.gif (so all themes have it by default)
- gallery module: added css for .ui-autocomplete-loading (copied from .g-loading-small in wind,
but without !important so other themes can override it)
- gallery module: updated upgrader.html.php to use new image (removes theme dependence)
- wind theme: removed outdated css for .ac_loading (not used in v3.0.5, either)
- server_add module: removed multiple argument from autocomplete (doesn't work well with it)