Streamline login sequence

The login screen user flow shall be simplified further from its implementation in release 4.9. 

On the first run

• the user has to authenticate themselves 
  • current twin text boxes kept 
  • remove the "submit"-button - use only the "next"-button in the SE-corner
• the user has to select whether to allow telemetry or not
  • there is no default, on the first run the user has to make the choice in order to proceed
• installer shall enable the "login"-button only when the user has filled in the authentication content as well as selected the telemetry setting.
• installer shall store the telemetry setting for later use. 

On later runs

• the user has to authenticate themselves (prefilled with stored login+password) 
• the user has the opportunity to change the "allow telemetry"-value (prefilled with stored setting value)
• installer shall enable the "next"-button, since all the parameters have been prefilled.