Item12661: Add support for nested MANIFEST files

git-svn-id: http://svn.foswiki.org/trunk@17106 0b4bb1d4-4e5a-0410-9cc4-b2b747904278
Item12661: Manifest path must be relative to base

git-svn-id: http://svn.foswiki.org/trunk@17107 0b4bb1d4-4e5a-0410-9cc4-b2b747904278