create domain class User
define user fields and methods
Merge branch 'develop' into feature/tasx-4-user-domain-class
implement password hash function
declare fields private instead of protected
fix groovy map syntax error

tasx-4
let groovy generate getter and setter for email
make private method User.hash static
omit optional semicolons
factor out sha256sum
pad sha256sum with leading zeros
unit test User.sha256sum

tasx-4
Merge pull request #1 from osu-mist/feature/tasx-4-user-domain-class

Feature/tasx 4 user domain class