Add a ronin wordlist-gen command

[postmodern]

Add a ronin wordlist-gen command that generates a new wordlist based on a password template. the password template syntax should be regex-like (ex: [:alpha:]{5,10}[:numeric:]{4}). It should also support embedding other wordlists into the password template (ex: ...#{wordlist.txt}... or ...[@wordlist.txt]...?).

The ronin wordlist-gen command should use the wordlist and chars libraries to combine multiple Wordlists and Chars::CharSet#each_string_of_length enumerators together:

Wordlist.open('wordlist.txt') * Wordlist::Words.new(Chars::NUMERIC.each_string_of_length(4))

We would also need to define our own parser code to parse the password template and generate the combined Wordlist expression.

[postmodern]

We might want to also add another separate command called ronin char-gen that only generates all Strings of a given length from a character set (see Chars::CharSet#strings_of_length).