Need a new color setting for the projector

[reiterl]

Needed by OpenSlides/openslides-client#3655

It should be a setting like chyron_background_color and should be in the projector model and needs update in the actions. E.g. chyron_agenda_item_background_color or chyron_background_color_2 or so, it should be called.

[rrenkert]

We also want a second text color.