Put LyXView on a diet, step 1: get rid of toolbars direct access from the core. Toolb...

Put LyXView on a diet, step 1: get rid of toolbars direct access from the core. Toolbar handling is a frontend thing; the goal is to progressively transfer that to the frontend.

* LyXView:
- getToolbars(): deleted.
- toolbars_: now protected. The goal is to transfer that to GuiView.
- openLayoutList(): new method. The core should not know how this list is displayed.
- showMiniBuffer(): new pure virtual method to show the mini-buffer.
- focus_command_buffer: deleted.

* GuiView:
- focus_command_widget(): deleted.
- showMiniBuffer(): implemented.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@19748 a592a061-630c-0410-9148-cb99ea01b6c8