Add possibility to interrupt and continue at a later time.

[filipeestima]

When the user presses Ctrl+C, it could show the last generated password, so the user can save it for use at a later time, when it's convenient. In order for this to work, you would need to implement a new option "-s or --startingPassword" and check if its use is possible, according to these parameters:

• Number of characters must be between minPasswordLen and maxPasswordLen;
• All characters must belong to the selected charset, being predefined or custom;
• If --passwordDictionary was used, then you need to find the password in there to continue, avoiding an endless loop. This may account for user error, when s/he started the search using one dictionary and continued later with a different one. Anyway, -c and -p should be mutually exclusive.

These checks are the important ones, to avoid making the software stuck in an endless loop. I think it would also be nice to use in scenarios where the user knows that the password starts with a certain string. Another possibility is to break the search space among various machines, each one at a different starting point.