Add new properties to user profiles

[Voltini]

This change introduces new properties to the profiles objects in database.

New properties

• profile::birthday which indicates the birthdate of a user. This could allow for new features to be implemented in nanachan.
• profile::pronouns for users who want to customize their pronouns.
• profile::graduation_year which corresponds to the year part of the old promotion property
• profile::n7_major which correspond to the major part of the old promotion property

Removed properties

• profile::promotion has been replaced by the previously mentionned properties