DirectHTTP: added support for head requests (to keep alive the connection)

git-svn-id: svn://svn.jdownloader.org/jdownloader/trunk@26460 ebf7c1c2-ba36-0410-9fe8-c592906822b4
Added Basic HDS Support. Encrypted HDS is not supported!

git-svn-id: svn://svn.jdownloader.org/jdownloader/trunk@26461 ebf7c1c2-ba36-0410-9fe8-c592906822b4