Small Bugfix

[h3]Changes:[/h3]

• improved method of calculating employee salaries
  
• corrected assistant's working hours when working first shift outside regular schedule
  
• a mark (green background) has been added to the info panel indicating that the assistant is working the first shift instead of the scheduled one
  
  Note: if the assistant works on a day off, this is not displayed on the info panel, but the time on work is visible and the salary is calculated correctly.