TypeDesc: Added TIMECODE and KEYCODE vecsemantics.
Docs, python, and tests for TypeDesc timecode and keycode changes
EXR: Support lots of additional metadata.
Uses the new VECSEMANTICS to tag SMPTE timecodes and keycodes.
DPX: Added smpte:KeyCode and smpte:TimeCode attribute handling
Merge branch 'timecode' -- add TypeDesc semantic hints for timecode/keycode