#6 Add support for cue-files

[Frank T. Rambřl]

Some mix CDs are in a cue/mp3-format where the CD is
ripped to just one large mp3-file to avoid a sound gap
which would not sound good on a mixed CD and the
tracks position in the file is given in the cue-file.

Players like foobar is capable of reading the cue-file
and supports skipping to tracks/positions in the large
mp3-file.

Would be nice if edna could support this in some way.