Provides methods and attributes relating to staff.

The following operations are supported. For a formal definition, please review the Service Description.

• AddOrUpdateStaff
  Add or update staff.
• GetSalesReps
  Gets a list of sales reps based on the requested rep IDs
• GetStaff
  Gets a list of staff members.
• GetStaffImgURL
  Gets a staff member's image URL if it exists.
• GetStaffPermissions
  Gets a list of staff permissions based on the given staff member.
• ValidateStaffLogin
  Validates a username and password. This method returns the staff on success.