Make behaviour the same as normal database services again

[daffl]

I have some changes for feathers-authentication/client incoming which does not require feathers-localstorage to behave differently than the normal feathers-memory. This reverts the changes we had to do and closes #6.

[ekryski]

We'll need to test this React Native before we merge it.

[daffl]

This should work in RN as well since those changes were only hacks to work with arbitrary ids and creating when doing an update.

I think for authentication we should go back to a transparent storage abstraction like:

// use memory be default
// use localStorage
app.set('storage', window.localStorage);
// use AsyncStorage
app.set('storage', asyncStorage);
// use custom store
app.set('storage', {
  getItem(key) {},
  setItem(key, value) {}
});

For user and token storage so that we don't have to hack the behaviour of what is technically supposed to be a standard Feathers database service.

[ekryski]

:shipit: