Feature/sha512

[mvo5]

This is a request for feedback, not yet a fully ready pull request.

It adds a nodejs cli mode to get the password (prototype only for now) and updates the code to prepare for using sha512 instead of sha1 (as its much harder to crack, some numbers in http://arstechnica.com/security/2013/05/how-crackers-make-minced-meat-out-of-your-passwords/).

If you aggree with the general direction I will continue and add a option to select the cypher and use sha1 only for backport compat.

[mvo5]

The sha512 support is working on my system now.

I also added a UI to select the hash algorithm for backward compatiblity and changed the default to sha512 and len 14.

Feedback welcome and thanks for creating this extension in the first place.

[mvo5]

The node cli part needs work as the password should obviously not passed via the commandline, that is just a proof-of-concept.