[ENH] cart: A few more params for the cart module, showItems, showCount and checkoutURL, plus fixes to support the module when in a wiki page

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@49801 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] login: Don't show facebook login button if already logged in

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@49802 b456876b-0849-0410-b77d-98878d47e9d5