Update loopback-core API docs for promises

[davidcheung]

Parent: /issues/1409
Related: strongloop/strong-docs/issues/63, strongloop-internal/scrum-loopback/issues/615

common/models/user.js
Instance Methods

• User.prototype.hasPassword
• User.prototype.verify Need update callback fn
• User.prototype.createAccessToken

Static Methods

• User.login
• User.logout no param except err
• User.confirm no param except err
• User.resetPassword no param except err

common/models/application.js

• Application.register Need update callback fn, this.create(props, cb);
• Application.resetKeys no param except err, this.save(cb);
• Application.authenticate

lib/persisted-model.js

• PersistedModel.replicate how to read Array with datatype like Change [] from callback?