minWorkers/maxWorkers ambiguity

[kwiatkk1]

The minWorkers option is only respected when initially reporting pool readiness, but should also be treated as a number of workers that the pool needs to keep running all the time, i.e.:

• on any accidental worker termination, pool should boot a new worker immediately (if minWorkers number is greater than the current number of healthy workers)
• a planned worker exit (for example as a result of WorkerEndurance value exceedance) should result in a spawn of a new worker before starting the process of termination the exhausted one (maybe even at cost of some extra calls above declared endurance).

[yurynix]

I think that somewhat handled in #62