Rewrite start

As yet, there are problems with removing empty tracks
Remove works Sort doesn't

Had to revert to rebuilding a list to get remove empty to work. Still
have no idea what is stopping Sort working. Some sort of NoneType
complaint.
Sorted works

Sorts by the text of the time tag from the first point.
Incorporate removedupes into removeempty

Function 'removedupesempty' now removes empty tracks and duplicate tracks
Merge remove dupes, remove empty and sort

One function, prepare(), now removes duplicates, empty tracksegs and
returns a track list sorted by timestamp of track's first point. Tracks
and tracksegs are synonymous.
Quiet mode

Added a quiet mode switch which silences the reports to STDOUT. Boolean
variable is called 'quiet' in main().
Rewrite complete

Goals achieved of removing duplicates and sorting tracks. (The overhead
of sorting is so low, I sort everything that comes in - why not?).
Also retain former functionality of cropping first and last trackpoint
as an option, ignoring tracksegs under a minimum number and ignoring
empty tracksegs.