The counters labelstring patch. Part 3: adapt some layout files and documentation

	* numarticle.inc:
	* numreport.inc:
	* stdcounter.inc:
	* stdsections.inc:
	* stdstarsections.inc:
	* stdclass.inc:
	* scrbook.layout:
	* amsmath.inc: adapt: remove most of the LabelString in layouts,
	add the necessary stuff to counters.

	* lib/doc/Customization.lyx: document the new stuff.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@19604 a592a061-630c-0410-9148-cb99ea01b6c8