fix(avatars): add profile server client to proxy remote images

Fixes #1458.
Fixes #1447.
Fixes #1469. It fixes the client portion, at least. The server depends on https://github.com/mozilla/fxa-profile-server/issues/31.

Not sure if we want to merge until the server side is ready.
Ugh, yeah maybe. `t`, as such, is kind of a hack. They way gettext and extraction are intended to work, `t` or whatever we call it would actually perform the translation, rather than just act as a stand in. If we want to go through the trouble of creating a module for it, maybe we should just use the translation module instead?