Introduce limit for oak.removeCollisions()

Currently the utility method in oak.removeCollisions() attempts to remove all collision markers for a given clusterId. With many collisions this can be a rather expensive operation that is difficult to schedule for MongoDB. I've seen cases where removing all collisions during DocumentNodeStore initialization was blocked for a very long time on the update call to MongoDB. On the MongoDB side the operation was retried many times because it conflicted with other concurrent updates on the same document.

The method should have a third parameter that limits the number of collisions to remove in one call.