-w and -U options, usage of "dust" block-tracks

The option -w (for line width) and -U (for uppercase) have been added
to DB2fasta and DBshow to give the use greater control of their .fasta
output.

If one has computed block "dust" tracks,
e.g. "DBdust DB.2", but not rolled them all together with Catrack,
commands like "DBstats DB.2" and "DBshow -d DB.2" still work by
accessing the block tracks.