[Feature/Improvement] Add ability to set a timeframe where this plugin does not turn on the light

[martinseener]

Add the ability to set a global or project specific timeframe where the plugin does not turn on the light, for example at night, when there is no one in the office to switch it off again.
Timeframe should look like two 24h dropdown-fields for a start and end-time with 30min gaps between them.