Added FileManager DLL and cleanup code

<SRS> SRS02 : Employee Management </SRS>

<Changes>
 - Created FileIO for reading and writing files
 - Created FileManager to use FileIO
 - Set up Trenser.FileManager as a DLL
 - Linked DLL with Trenser.Zenvy project
 - Fixed duplicate function issue by marking deactivateEmployee as inline
 - Cleaned up unused methods in controller and service
</Changes>

<Review>
Smitha Mohan
</Review>

Trenser.Zenvy/Trenser.Zenvy/views/MenuHelper.h

@@ -76,7 +76,7 @@ inline std::map<int, std::shared_ptr<const Employee>> listEmployees(const std::s
     return employeeList;
 }
 
-void deactivateEmployee(const std::shared_ptr<ZenvyController>& controller)
+inline void deactivateEmployee(const std::shared_ptr<ZenvyController>& controller)
 {
     auto employeeList = listEmployees(controller);
     if (employeeList.empty())