Hold Manager: Intelligent VSL Choices

[AndyTWF]

At the moment, the VSL display logic for holds is quite basic with regards to "conflicting" aircraft... don't include in the display if all of the following are true:

1. It's not assigned to "this" hold
2. It's assigned to hold at another navaid.
3. It's within the confines of a published hold that is "deemed separated" from the published holds of "this" navaid.

This neglects one key variable, aircraft that are departing (e.g. aircraft holding at Biggin vs Detling departures). In this situation, so long as they're under positive control: we should really trust other controllers to not crash things (at least up to a point). Some thoughts:

1. Predictions

Use ES's "position predication" classes to compare the "conflict" to other aircraft in the hold. If they're never going to get close to each other in the next, say, 3 minutes, filter them out.

2. Tracked aircraft

If the AC is tracked by someone, we could reduce the VSL insert distance a bit - trusting the controller to not deliberately conflict aircraft. Non-tracked aircraft should always be inserted into the VSL as they could be considered as renegade until proven otherwise.

[hazzas-99]

@AndyTWF e.g. this a/c 10 miles away from LOREL stack displays, but probably shouldn't!