[ENH] Add div#middle and footer#footer to social layout so themes won't miss related style details of other layouts.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/13.x@52346 b456876b-0849-0410-b77d-98878d47e9d5
[ENH] Adjusted indentation; no code changes.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/13.x@52347 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] Some themes expect #middle to have class="middle".

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/13.x@52348 b456876b-0849-0410-b77d-98878d47e9d5