Added logic to send a second HEAD request if initial status is 406 - not...

... acceptable since that indicates the content might be link protected and RANGE header is not allowed.  Simplified the if clause around using time seek range values for dtcp and non-dtcp content.  Added methods to convert between npt and bytes to be used by dlna_src_handle_query_convert().  Adjusted log message levels.  Changed name of method from "formulate_extra_headers" to "adjust_http_src_headers" since the method will now set property of souphttpsrc so that RANGE header is excluded in additional to adding extra headers.  It will now add Range.dtcp.com header for DTCP encrypted content.