added FAQ on limits and conscious departure as optimization

the phrasing is still a bit awkward, so this is merely intended to start the discussion

would appreciate input from @stilkov, @tillsc, @cdent and whoever else might care

aside: I tried to work what I consider a powerful quote from @cdent into this, but it didn't quite fit in. Any ideas where we might put it:

> ROCA is a distillation of ten years of web development experience.
> the answer doesn’t answer the question

True, actually. So ... let's change the question. (e.g. "Is ROCA a fascist regime?")

> I’m not entirely sure this actually really adds anything other than some
> common sense statement true for any architecture.

It doesn't, really - however, many people expect things like ROCA to be comprehensive and get all confused when they hit a wall. This is meant to explicitly concede that ROCA is not a silver bullet, thus defusing misguided discussions.