This commit cleans up everything related to singleton. The other important change...

This commit cleans up everything related to singleton. The other important change is that lyx::dispatch() and lyx::getStatus become _the_ official way to use LyXFunc equivalent methods.

* lyxfunc.h:
  - theLyXFunc(): new function in the global namespace.
  - lyx::dispatch():  new function in the lyx namespace.
  - lyx::getStatus():  new function in the lyx namespace.

* bufferlist.h:
  - theBufferList(): new function in the global namespace.

* Clipboard.h:
  - theClipboard(): new function in the global namespace.

* Selection.h:
  - theSelection(): new function in the global namespace.

* FontLoader.h:
  - theFontLoader(): new function in the global namespace.

* FontMetrics.h:
  - theFontMetrics(LyXFont const &): new function in the global namespace.

* Application.C: implements the functions defined above.

* LyXView.h:
  - getLyXFunc(): deleted.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@15298 a592a061-630c-0410-9148-cb99ea01b6c8