Created FlightPlan class and removed separate speeds + altitude in waypoints
Added maximum number of aircraft + removed DefaultObjectCreationRate

- The code from DefaultObjectCreationRate is now in FlightPlanGenerator
Flight plans no longer use entry point which cause an imminant collision
Made the config options in FlightPlanGenerator changable

- Also removed the now unnecessary minimum time between aircraft
Refactored all the game constants into a Constants class
Moved random methods from FlightPlanGnerator to Utils
Fixed turning issues created by previous commits
Merge pull request #13 from sepr-hou/new-flightplan-generation

Big flight path generator + constants refactor / rewrite