Added succesfully listener 'tab monitor' that update the unified search widget
and this, with a new getter property, knows that
the filter can be applied or not into the current tab, auto-disabling
filter by changing to search mode, and restoring to filter when again in a
tab that allow it.
It remains check too current view (if need), like a change to a 'root'
(aka 'account central') folder or similar that cannot be filtered (not sure if need),
and check the new property for any handler that try to do filtering or change to filter
mode.