* Gui.h: new closeAll() pure virtual method.

* Gui.h: new closeAll() pure virtual method.

* qt4/Alert_pimpl.C: make sure the proper Qt attributes are set.

* GuiApplication::quitLyx(): add the "force" argument to the funcRequest.

* GuiImplementation:
  - GuiImplementation(): remove the signal connection. This was triggered after the LastWindowClosed signal so was not useful.
  - cleanupViews(): renamed to unregisterView() and handle the WorkAreas as well.
  - closeAll(): new method (from LyXView).

* GuiView.C
  - clean up the includes order.
  - closeEvent(): make sure that theBufferList().quitWriteAll() is called if last window closed.

* lyx_main.C / LyX::quit():
  - remove noAsk argument
  - delete bufferList::quitWriteAll() call (this is handled in the frontend).
  - delete Session stuff (ditto)

* LyXFunc::dispatch()
  - LFUN_LYX_EXIT: close all window before exiting from user command (as opposed to last window closed).

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@15535 a592a061-630c-0410-9148-cb99ea01b6c8