Replace the install wizard "Connect Sign up" Form by new io one

Currently the wizard shows the sign up form current_signup.pngby the new io one (new_signup.png), without calling the nuxeo io creation

• create a connect account
• create a Studio trial
• Register the Nuxeo Platform instance
• being able to register if already an account ("If you want to link an existing Nuxeo Connect account to this installation, click here" that leads to already_account.png)