[#10] Basic stable version of registration form. Added basic data verification, new field in user model called nickname, added new unique field "VARCHAR(32) nickname" in Database, edited index.html to welcome user with a nickname instead of an email.
[#10] Updated style and fixed bugs of registr_form
Merge pull request #17 from zpidreamteam/feature/registr_form

Pull request / registr_form to develop