* src/text3.C
(LyXText::dispatch): An empty argument of LFUN_LAYOUT is now allowd
and means the default layout of the text class
* lib/images/layout.xpm: New image for default layout
* lib/Makefile.am: Add new file
* development/scons/scons_manifest.py: ditto
* lib/ui/stdtoolbars.ui: Add "Deafult" layout button to the extra toolbar
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/branches/BRANCH_1_4_X@15953 a592a061-630c-0410-9148-cb99ea01b6c8