Set timecode to "now"

[Rick Botman]

Setting the timecode for writing currently requires specifying the start time as a string:

-timecode hh:mm:ssSEPff

It would be convenient in non-programming applications if the timecode start time could be specified as "now", which would be interpreted as the system clock time at runtime.

To be comprehensive, perhaps the "now" argument could have an optional trailing character to indicate drop or non-drop timecode. For example:

-timecode now;
-timecode now:

I'd suggest that omitting the trailing character would default to non-drop.