JBIDE-16246 : (un)select/edit multiple dependencies at once

New UI improvements in Dependency Conversion wizard :

- added Select/Deselect/Edit... context menus on right click
- added Edit... button
- Selecting multiple dependencies and clicking on Edit... will only allow
  edition of the scope

  See the changes in action :
  http://www.screencast.com/users/fbricon/folders/Jing/media/fcd47ccf-b190-41c8-bfb3-074697c883da

Signed-off-by: Fred Bricon <fbricon@gmail.com>
Fix test regression caused by NPE in MissingEndorsedLibMarkerResolutionGenerator

Signed-off-by: Fred Bricon <fbricon@gmail.com>
Fix test regression caused by NPE in AppClientDependencyConversionParticipantTest

Signed-off-by: Fred Bricon <fbricon@gmail.com>