Add optional value to list option.

It now takes a number of directories to display
refactor directory parsing code etc
remove reference to .bday
extract creation of bday name
updates to read the .bday directory not the directory being watched
fix bug in display_files where output of sort wasn't being used
Fixed bug in CreationTable#remove_file

The bday directory prefix was not being prepended to the filename.
whimped out and left out trying to TDD the sorting of files