Refactored how updates are handled, now when there is a change the client is told to update there local copy with the specific change, rather than resend either the whole list of employees information, or the whole list of shift information. This change to updates should make changes to the staff or schedule more efficient especially when there are multiple clients.
In coming data from the server is now stored in HashMaps where the key is either the shift or employee IDs, and the value is of Shift or Employee classes.
All the methods in this class were made to help with these 2 changes.
Cleaned up warnings.

Changed update implementation for employees so rather than sending the whole list of employees when there are staff change, the server sends a message to all active clients to add/remove them locally. Also, changed all exception variable names to 'exception', and cleaned up warnings.

Fixed bugs with that caused in consistencies with message sending between client and server. All employee data should be updated to all clients when employee data is modified in the database. The client should have an updated copy of employee information.