Swap-window instance with narrow window width

[akmaralAW]

Currently, db-cbs can not solve the swap-window problem with window width = 0.6 with more than 3 robots (checked with window4_unicycle.yaml).
It runs very long, and in the end the script terminates with error dist < delta, VIOLATION which arises from dd_Astar.hpp.

It can solve if the window width = 1.

[akmaralAW]

I can take it.

[whoenig]

Not really urgent; let's just focus on the paper for now. We are still missing some of the results and sections.