Cleanup of the Toc model and controller: The objective is to let the View (TocWidget...

Cleanup of the Toc model and controller: The objective is to let the View (TocWidget) decide which kind of list it want to show. The type given by InsetCommandParam() (as read by the controller (ControlToc) then just becomes a hint to the View. Most of the commit is about getting rid of the controller maintained list of types.

* TocBackend
  - addType(), types_, types(): deleted.

* ControlToc
  - tocs(): new
  - selectedType(): access to selected_type_
  - initialiseParams(): transfer code from QToc::update() and look for selected type.
  - getTypes(), getContents(): deleted

* QToc: do not maintain current type. Get the info from the View.
  - setTocModel(): deleted

* TocWidget: always pass the currently selected type to the model/controller.
  - setTocModel(): new slot.
  - updateGui(): transfer code to setTocModel().

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@17455 a592a061-630c-0410-9148-cb99ea01b6c8