Allow remote memories

[jkomoros]

Currently memories are always local to a profile. But ideally you shoudl be able to 'dial' a remote memory, and they should possibly require an access key to read and/or write.

At that point it's basically a polymath instance (although with the ability to write to the memory sometimes)

An extension of #23.

Needs a way to allow read and write privileges on remote memories. (And also to make sense of read/write privileges on local memories)