Add support for linking items via dnd.
Add support for linking items via dnd.

svn path=/trunk/KDE/kdepim/akonadi/akonadi_next/; revision=1022341

lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi