Use input_datetime.morningtime as starttime

[Stromber03]

Hi,
It could be a nice thing to use an input_datetime as starttime attribut instead of time and/or sunrise.

For exemple,

    - { starttime: " input_datetime.morningtime", name: nuit, light: scene.couloir_rouge }
    - { starttime: "sunrise+01:00", name: jour, light: 0 }