[models] removed old columns from source code
[models] Type in for loop
[models] Added relationship for manager

Added a forgein key constraint and a sqlalchemy relationship between the
manager and the employee.
[models] EventToDict will not call on userToDict

Changed the default behavior of EventToDict to not call userToDict
retursively.
[models] Renamed the employee relationship

Renamed to users employee relationship to be employees.
[models] Implemented get_managers_* functions.

Implemented the get_managers_* functions using the new database models.
[docs] Started to add detailed docstrings
[docs] Added the docstring for the helper views.