New mode for entering track marks on recorded MDs

[fijam]

Consider adding a new mode for entering track marks at predefined time-points on an already recorded MD.

[fijam]

This could be thought of as an enhancement of #13, which requires track marks to be already present on the MD.

EXTM3U format allows for saving track duration in the playlist like this:

#EXTM3U
#EXTINF:180,Artist - Title
Artist - Title.mp3

However, while Foobar2000 can save a playlist in this format (after ticking a box in Advanced options), it will ignore this additional metadata when loading a playlist... Nothing I can do about it at the moment.