Update UI based on login session

[tanbt]

• Must a clear event-hierarchy to send and load the login user data.
• Careful with the render order (check Network request loading's order)
• Ready() is executed after all other html and script are gone through.

[tanbt]

PolymerPractice\my-profile\src\my-profile-app.html:

• After this file is ready, load the user from local storage, then set it to the user property
• [optinal] The user property is already observed by _computeShouldRenderUser(user) for any changing
• This user property then is bypassed to child component: <my-profile-home name="home" user="[[user]]"></my-profile-home>