Bug 413975 - [Viewers] Add generics to the ViewerFilter
Bug 413978 - [Viewers] Add generics to the ViewerComparator

Added generics to the ViewerFilter and ViewerComparator to allow a
typesafe use of the viewers framework.

Includes also updates in the AbstractTableViewer and AbstractListViewer

Change-Id: I4fd80e2866b27fab1a563ec17eb925b2e6b3bd3c
Signed-off-by: Hendrik Still <hendrik.still@gammas.de>