Part of #2017207: [meta] Complete conversion of users to Entity Field API.
This converts the following property to methods:
- status to isBlocked(), isActive(), block() and activate()
- mail to getEmail()
- login to getLastLoginTime()
- created with getCreatedTime()
- name with getUsername()
- roles with getRoles(), addRole(), removeRole(), ..
- signature and signature_format with getSignature() and getSignatureFormat()
- pass with getPassword()
- timezone with getTimezone()
- access/timestamp (session stuff) with getLastAccessedTime()
- langcode and preferred langcode with language() and getPreferredLangcode()
