Improved JavaDoc
Added explicit symmetry to the way panels are created and destroyed (both are done by PanelManager via BeanFactory now). Refs UF-99.

The TemplatedPanelManager and the JSWorkbenchPerspectiveActivity need to be modified similarly to the NSWEPanelManager
and the AbstractWorkbenchPerspectiveActivity before this work can be merged.

Also, some new unit tests are required before this is merged upstream.