Major update of traffic manager and AI related airport facilities.

Major update of traffic manager and AI related airport facilities.
- Moved AIModels/Traffic Manager related AI functions to a new file
- Rewrote the traffic manager so that the containers use pointers to
  objects instead of the objects themselves, which will allow for a
  more flexible memory management.
- Rewrote parts of the airport groundnetwork code, also because the
  stl containers now contain object pointers instead of the objects
  themselves.
- Fixed an uninitialized iterator in the AI distance tracking code
- Fixed flawed logic in some of the traffic controller's while loops
- Added a tower controller, which paces take-off behavior of AITraffic
  in a more realistic way.
- Various other minor fixes and fine tuning.