- Make it self-contained, instead of having its code
  spread across ToolBarManager.
- Base it on svt::ToolboxController directly, since it
  uses nothing from GenericToolbarController.
- Move the code from dtor to dispose method.
- Call ToolBox::SetItemDown to make the button work on
  a second click.

Change-Id: I5b38ef532ba40ef0ac31bc53de5b6be4ccd1a118
Reviewed-on: https://gerrit.libreoffice.org/33982Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Maxim Monastirsky <momonasmon@gmail.com>