Item12481: added opensearch support

also:
- removing %CLEAR% element in favor of a clearfix class for the container
- renamed natRevision to foswikiRevision
- customato: improved heading colors



git-svn-id: http://svn.foswiki.org/trunk@17572 0b4bb1d4-4e5a-0410-9cc4-b2b747904278