Allow multiple options for picture_output

[utouchgrass]

Currently you can just use one: e.g. picture_output best

I want to save a picture when the event starts while keeping current behavior, so I want to use:

picture_output first,best

OR

picture_output best
picture_output first

[chegancasb]

Not a solution but a work around: use on_event_start to call a script that calls the camera image endpoint.