Run ets_fiber_assigner iteratively to avoid trajectory collisions

Currently the ets_fiber_assigner only avoids endpoint collisions of cobra tips with other tips or elbows. By running a provisional solution through the the collision simulator from ics_cobraOps, we can detect trajectory collisions as well. With this information, we can add constraints that disallow simultaneous observation of the problematic paits of targets and re-run the fiber assignment step.

There are a few caveats to this approach that need to be kept in mind:

• we do not know how many iterations will be needed to arrive at a configuration that has no more trajectory collisions. Depending on the setup in question, there may be quite many.
• the collision simulator only simulates a single realization of the Cobra movements (as far as I know). Given the stochastic nature of the movements, this does not exclude trajectory collisions when repeating the fiber movements on the real telescope. This can most likely be addressed by adding some sort of safety margin, but this needs more discussion.