[dcc2] Multi headers + metadata

[Craig Edwards]

>Content type (not all systems determine a file's type by its extension, 
>and some extensions are ambiguous)
>Codec (for audio/video)
>Length in seconds (ditto)
>Origin (web site or person who supplied the file)
>Version?
>License/copyright notice?
>

These of course would be optional but the implementation could fetch them from id3 or header etc tags of whatever file its sending to the user i suppose?