Fix shelf numbering
Fix shelf numbering

id must be unique. So if we have 2 zones with 1 shelf in each, hide 1
zone and add a new shelf, it must get id "hidden shelf" + 1

SVN revision: 45563

rvandegrift/e,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,rvandegrift/e,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,tasn/enlightenment,FlorentRevest/Enlightenment,tasn/enlightenment,FlorentRevest/Enlightenment