crumbs/persistenttooltip: a new Gtk+ widget for use in Hob

crumbs/persistenttooltip: a new Gtk+ widget for use in Hob

The Hob interaction design calls for a top level widget which shows a
persistent tooltip. This tooltip will not disappear until the user
explicitly closes it.

This allows us to provide clickable hyperlinks, longer instructions and
deeper information in the tooltips.

Note: by design the tooltip should dismiss when the user clicks off it,
this implementation does include that functionality. It's a to do item.

(Bitbake rev: b310fd429150d3a96ecde477934fffad4b4031da)

Signed-off-by: Joshua Lock <josh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>