Add multiuser support

Currently, this uses anonymous sessions. You log in to your instance, and you
get associated with a session. Your client information and account information
are persisted (created only if needed, reattached if not). Passwords are never
stored, only access tokens.

brutaldon/forms.py

@@ -3,7 +3,7 @@ from django import forms
 class LoginForm(forms.Form):
     instance = forms.CharField(label="Instance",
                                max_length=256)
-    username = forms.CharField(label="Username",
+    username = forms.CharField(label="Email",
                                max_length=256)
     password = forms.CharField(widget=forms.PasswordInput())