[mxf] Add complete support for AVID MXF files (clip wrapped)

Submitted by owe..@..wg.com

Link to original bug (#561922)

Description

I've generated some MXF files in Avid for testing. Each one is a set of color bars with text over them like "Avid NTSC DV25 29.97" or whatever else the codec is.

I got a little confused, so the text on the titles may be incorrect. Sorry about that. However, the filenames are correct.

Here are the files:

Avid 1-1 1080i 5994 1 sec.mxf: Avid 1:1 codec (totally uncompressed, should be easy) at 1080i 59.94 fps for 1 second. this is an interlaced codec, upper field first.
Avid 1-1 1080p 2398 1 sec.mxf: Avid 1:1 codec at 1080p 23.98
Avid DV25 NTSC 2997 3 sec: regular 29.97 NTSC DV video for 3 seconds
Avid DV25p NTSC 2398 2 sec: progressive 23.98 DV video for 2 seconds

I can generate all sorts of wonderful codecs too, including DNxHD and all the old avid codecs (15:1, 4:1, etc etc).