TaskPreviewDeleg moved to new dragging architecture, fixes

--TaskPreviewDeleg was cleaned a bit more. Now remains its
separation in three different classes
--An issue was found in counting windows in workareas, if
the workarea has more than 6 windows doesnot increment any
more windows number (maybe a new taskManager function can
help with this)
--The Filtered Task Model tried to be used with the Workareas
but the perfomance I think was dropped a lot