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.
But the answer doesn’t answer the question. I’m not entirely sure this actually really adds anything other than some common sense statement true for any architecture.