Store User object in Dash Auth object

[jsh2134]

Store the SolveBio user object in the app authentication object. This would allow apps to save a User lookup

Set somewhere here: https://github.com/solvebio/solvebio-python/blob/master/solvebio/contrib/dash/solvebio_auth.py#L169

[davecap]

The apps are stateless though, do you mean cache user object keyed on the auth token?