Fix break ordering

[jcoupey]

Issue

Fixes #385

Tasks

• Patch TWRoute::order_choice
• Update CHANGELOG.md
• review

[jcoupey]

The previous commit does a good job avoiding the problems described in #385, and from a heuristic standpoint it makes sense to favour including pickups first whenever possible, because that's the best way to save room for the upcoming matching delivery.

On the other hand, this simple fix still has a bias: think a situation where both pickup and delivery are doable after the break (B -> P -> D is valid) and pickup looks OK before break (P -> B is valid). Then with 809bd20, the latter will be chosen but both P -> B -> D and P -> D -> B may turn out to be invalid.

This instance with a single vehicle, break and a single shipment has time constraints designed especially to reproduce this situation. When solving with 809bd20, both pickup and delivery turn up as unassigned whereas the shipment could be assigned in a valid way after the break and we simply fail to lookup this option.