Remove extra empty lines from services.template
Add User.getCurrent, persist accessTokenId

Add new method User.getCurrent() that returns data of the currently
logged in user or 401 when no user is logged in. Extend LoopBackAuth
to keep currentUserId.

Modify LoopBackAuth to persist all properties in `window.localStorage`.
Implement "rememberMe" option for login.

Modify User.login response interceptor to save the access credentials
to `sessionStorage` when `params.rememberMe` is `false`, localStorage
otherwise.

Describe this new parameter in User.login documentation.

Refactor LoopBackAuth to decouple property setters and the persistence
layer, add `LoopBackAuth.save()` to explicitly persist changes.