Implement Cloneable and override equals() for Coord and Course
Fix errors in test cases
Bug fixes in Vessel class

- Must convert time to seconds before calculating new coordinates!
- Course never changes unless explicitely updated (according to the
teacher)
- Make copy of data received in update()
- Check that we never update() for a lower or equal timestamp to
lastTimestamp
Add test case for UpdateData JSON serialization
Fix Netstring decoding in ConnectionServer
Fix major bug in Vessel class

getCoord() should never change the state of the vessel, it is an
accessor!
Fix ConnectionServerTest threading