as a user I want a offline message more user friendly

[fabienmoyon]

#### currently

For example in INBOX SPA, a message is displayed BUT this message is done and manage by the INBOX SPA and displayed in the main page so I lost my context page and this message is not so explicit when I'm offline or when I have a network error.

expected

Like in an other app :

• keep the current page and the context
• display the message on top and less intrusive to the user
• have a component more intelligent how can do/try some actions and display some buttons

• This component can be done in the common libs to be used by each SPA and can also be a good base to manage other stuff like the quota banner or the vacation banner in the INBOX context.