Bug 1100945: adding a PasscodeHelper

This should do as an initial draft.
Looking forward to any kinds of feedback, especially lines 70-73 and 88-100. :)
For a function you can do this:

    _makeAndCompare(salt, iterations, algorithm, ...)

It's better than destruct in the function, since user would never know what the values should contains, especially when it's a 'array with meaningful index'.