Use sqlalchemy.ext.hybrid.hybrid_property instead of scqlalchemy.orm.synonym

[eoyilmaz]

User Story

As the developer of Stalker I want to utilise the new sqlalchemy.ext.hybrid.hybrid_property instead of scqlalchemy.orm.synonym as it is more suitable then synonym's in some of the use cases.

Acceptance Criteria

1. Replace scqlalchemy.orm.synonym's with sqlalchemy.ext.hybrid.hybrid_property where the synonym is used to create a getter and setter without changing the attribute name.