Improve SvSimpleTable class

It is possible to order columns. This is set in Expert Configuration
dialog. The header's itembits weren't set correctly therefore mouse
click handler didn't do anything. The comparsion was slow on big
table.

Conflicts:
	include/svtools/treelist.hxx
	svtools/source/contnr/simptabl.cxx

Change-Id: I7e1301d40433ef45b3d0a3fb300909345ede9d4d
Reviewed-on: https://gerrit.libreoffice.org/12070
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>