should persistenceDir default to being current working directory or something under `~/.brooklyn/` ?  i was thinking the latter -- though maybe that should just be the default.

i think in practice for us it's important to be able to run mulitple brooklyns on one box and not have them step on each other's toes, even if we didn't change the settings, and we ran them from the same dir.  that may be a little irritating but i guess they'll have to collaborate somehow for that to work, e.g. by storing their management timestamp in the filesystem and coordinating who manages using that.  solveable, with a little bit of care.  can talk F2F on this, yeah?