Fix Content_Tagger::getCloud method when filtering by objectId.

This could never have worked properly without knowing the typeId
of the objects. Make it so.
Add helper method to get tag usage in a subset of objects.
Improve Core_TagBrowser's related tag functionality.

If we know the objectIds we are interested in, use those to perform
a more efficient 'cloud' query instead of iterating each tag
and searching. Also allow concrete tagger classes to override
the strategy used to obtain the related tags when it is more
efficeint to do so.
changes
Further improve related tags functionality.

Allow for providing a default list of object ids to be used when
there is no current tag search in progress. Saves having to
query the tagger for *each* tag in order to get the tag counts.
Re-enable tag browsing.
Reset the tasklist right before we use it, not earlier.
Pass the list of task uids displayed in the current view.

Avoid multiple tagger queries, and fixes displaying tags not shown
in the current completed filter.
Bump version required.
changes