feat(avatars): profile images

Getting there! Feel free to start looking @shane-tomlinson @pdehaan.

Still needs:
- [ ] profile-server client
- [ ] progress indicator screen
- [ ] unit tests for camera view
- [ ] unit tests for cropper widget
- [x] circular overlay on cropper
- [ ] functional tests
The exploding `Session` has been on my mind a lot lately, I've been trying to slim it down. Now that we are adding more model-like stuff, it makes sense to create distinct models for our own future sanity. We can stuff things into `sessionStorage` or `localStorage` to handle page reloads.