Fixed some bugs that would cause edited shifts to return nothing, and the edited availability to return nothing.

After a change in the database that made email addresses unique, caused a bug where new employees on the app to not be added after the first one.

Fixed a bug where isManager wasn't properly evaluated, and changed how positions in the employee are separated.

Added a claus that checks if a position is removed from all employees during the "removePosition" case.

Fixed an issue with added positions if they didnt exist in the position table, and a bug after removing the last position for an employee then adding a new one.

Now supports position data. Made the made changes to some cases and methods to make distinctions between employees trained positions and positions in general.

Shifts now have a position field, that the schedule classes methods are updated to take positions and return position data.