Allow dashes in numbered wordlists

[ulif]

Numbered wordlists denote dice throws with a sequence of dice-numbers like this:

123456  some-word

This is not a problem, as long as you expect ordinary six-sided dice to be used. But some dice have 10 or more sides. For instance 11111 with 12-sided dice could mean 11 followed by 11 followed by 1 or it could mean 1 followed by 11 followed by... you get the idea.

In short: 11111 might be ambigous.

To overcome this problem, we should additionally allow dashes in numbered wordlists:

1-2-3-4-5-6  some-word

such, allowing clear separation of single numbers in the sequence.

This change would not be a big thing for diceware as we do not interpret numbers in wordlist. We just have to detect them.