add new icon for webservice refresh

The web-refresh icon is used for a button on the toolbar of the journal
expanded entry to contain a palette of refresh buttons for webservices.

See journaltoolbar.py in https://github.com/sugarlabs/sugar/pull/62

The relevant feature request is:

http://wiki.sugarlabs.org/go/Features/Web_services
Merge branch 'master' of https://github.com/walterbender/sugar-artwork