Finish 'add' command so that it actually works
Add 'dispass list' command

Add dispass list command which is functionally identical to
the earlier command and arguments: 'dispass-label -l [--script]', but
with added '--dry-run' and '--silent' options.
Add 'dispass rm' command

Add dispass rm command which is functionally identical to
the earlier command and arguments: 'dispass-label -r', but with added
'--dry-run' and '--silent' options.
Rewrite 'help' command to use the new main class