Display user email based on admin configuration

User email is hidden across whole Zanata at the moment.

Require feature to allow admin to configure to display user email or not in Zanata.

API

• project contributors list - when configuration for display user set to true

• user service (private api for editor, /user/{username}) - when configuration for display user set to true

UI

• user profile page - when logged in and configuration for display user set to true