[FIX][ENH] categories: Add a pref so the object count can be disabled on tiki-browse_categories for large sites (over 40 seconds to load on one example site for instance)

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@48176 b456876b-0849-0410-b77d-98878d47e9d5