It matches other applications both in Windows and OS X. Users expect to press
the 'D' key to activate this button. Also, it's shorter.

Change-Id: I08f80fd9dbfbc5e2a5dc69ff2f72d55b80ccda5a
Reviewed-on: https://gerrit.libreoffice.org/10685Reviewed-by: Olivier Hallot <olivier.hallot@edx.srv.br>
Tested-by: Olivier Hallot <olivier.hallot@edx.srv.br>