media/cbsnews.lua: Rewrite parse function

media/cbsnews.lua: Rewrite parse function

Rewrite the "parse" function for libquvi 0.9+ series.
* Add CBSNews.{parse_optional,iter_streams,get_data,to_id} functions
* qargs.id would normally be optional, but required by CBSNews.get_data
* Add CBSNews.{parse_optional,iter_streams,get_data,to_id} functions
* Remove any now obsolete code (e.g. self.host_id)
* Update vim modeline

NOTES:

  quvi/lxp:find_first_tag will raise an error if something isn't found.
  This means that any optional media properties parsed using this
  function, will result in the script exiting with an error.  This is
  acceptable, although not ideal.

Signed-off-by: Toni Gundogdu <legatvs@gmail.com>