Portable install of Keybase client

I wonder if would be difficult to offer a "portable" install option, where you can just unpack a distributed file and keep everything inside a single directory.

Common use cases are keeping a portable USB drive with all your Keybase install, or in my case, a [QubesOS](https://www.qubes-os.org/) AppVM specific to Keybase, the same way I have one "vault" AppVM for gpg.

Right now, the CLI is already quite portable (I can extract it from the .deb package file, and run it "in-place"). But databases, configuration files and caches seem to be created on the user directory. For my QubesOS use case that is fine, as the AppVM is persisting all files in `~/`, including `~/.config`, `~/.cache`, etc.

Would that require code changes on the CLI and UI, or it is just packaging and preconfiguration?

Start by reviewing the CLI and UI installation paths, including how the package is unpacked and where databases, configuration files, and caches are written. Done would mean a distributed install can be unpacked into one directory and keep the Keybase installation data there, including for the stated QubesOS and USB-drive use cases.

Written by the indexing model from the issue text.