added getCurrentTarget, isCloseToEntry and getAvailableEntryPoints from
our previous project modified so that they are compatible
planes are now spawned only in available origins - not taking into
account planes on different altitude levels. Bug however - sometimes it
freezes when difficulty is selected.
bug mentioned previously fixed, planes are still spawned only from entry
points that are "available" - currently ignores altitude of planes. Will
make it somehow so that it takes altitude of plane into account and will
make entry point available to different altitudes
changed altitude list to static to be able to use it in array that
returns which altitudes for available waypoints planes can be created
in. Also wrote the method itself.
job done, refactoring to go
Refactoring + adding comments, will remove aircraft_list from Aircraft
constructor due to redundancy in next commit
got rid of aircraft_in_airspace as it was redundant - previously used by
INI as an attempt to make creatingAircraft fair.