Fixed a critical human error translating file bytes to hex instead of
ascii.
Fixed b0rken string -> byte[] and vice versa implementation.

Thank you, dear interwebs/lazyness!
Removed the last bit of cruelty in string conversions.
Updated the MD5 class with a public member to make it actually useful.
Created the User model/object, with password validation routine.
User model fully finished
UserManager partly implemented