preparing taskManager to be qml plugin
HUGE COMMIT but important for decoupling...

--all the files are almost ready for the qml plugins
in the qml plugins are going to be moved the following
taskManager, previewsManager, workflowManager(contains
the model, activityManager and workareaManager). Remains
only to separate the code that can not be moved to qml
plugins yet. This is just two hack classes (show widgets,
and find background for an activity)