[ENH] forums: If using WYSIWYG use the html part in process_inbound_mail if available. Needs to be purified (before parsing to wiki if wysiwyg_htmltowiki) as email html can be messy

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/13.x@52714 b456876b-0849-0410-b77d-98878d47e9d5