When hovering the mouse over a slide its name is displayed in a tooltip.
If you jump with the mouse from slide to slide the new tooltip is displayed
immediately.
Also remove unused member variables and make tooltip delay configurable.

Change-Id: Ia2347d81620f0ced437beaaeb49d8ad7f41e9333
Reviewed-on: https://gerrit.libreoffice.org/2969Reviewed-by: Thorsten Behrens <tbehrens@suse.com>
Tested-by: Thorsten Behrens <tbehrens@suse.com>