Add new helper method to accounts manager

A common test is to see if there are configured accounts. A new
method, has_configured_accounts, has been added to cover this case. A
unit test has also been added.
Add menu items to journal palettes for webservices

This patch adds UI support for interacting with online accounts from Sugar.
The relevant feature request is [1].

The new UI elements are added to the Sugar Journal Detail View toolbar:
(1) webservices are added to the Journal list view Copy-to palette and
to the similar palette on the Journal detail view toolbar.
(2) A palette of refresh buttons for all webservices are also added to
the Journal detail view toolbar. These buttons are enabled when the
webservice is active and insensitive when the webservice is inactive.
It also adds a new UI element to the Sugar List View palette: webservices
are added to the Journal list view Copy-to palette.

[1] http://wiki.sugarlabs.org/go/Features/Web_services

Depends on new helper method in https://github.com/sugarlabs/sugar/pull/3
Merge branch 'webaccount-ui' of https://github.com/walterbender/sugar into webaccount-ui