admin availability null error, can't navigate from staff -> sched (staff loads different panels) pop ups still need to be hooked up

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

Added a clause to the add shift method that checks the availability and makes sure that the start is later than the end.

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.