F2 or Enter can now switch to text edit mode.

Change-Id: I1aea09bd2fc4fa64db49b2037894082fe33af934
Reviewed-on: https://gerrit.libreoffice.org/23836Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>