Add new icon for web account refresh menu

The refresh-web-account-menu icon is used on the Journal expanded-entry toolbar. It
is used as a button to contain a palette of refresh buttons used by webservices.

This button is used in journaltoolbar.py as per [1].

The relevant feature request is [2].

[1] https://github.com/sugarlabs/sugar/pull/92
[2] http://wiki.sugarlabs.org/go/Features/Web_services