Passphrases are now hidden by default. Also added site name and custom salt to provide salting so different sites have different passwords generated from the same passphrase
Added username as extra salt as well
Cleanup and made the code web worker clean. If the code is in an environment where web workers are available (note that in Chrome they aren't when in file://) will use those to generate keys instead to prevent stalling the UI for 2 seconds. Still need to make sure we don't keep sending messages over to generate more when we're already busy since right now they pile up.