Yellow background for community_centre and social_facility

[kocio-pl]

Related to #2087.

I think it's safe to add community_centre (#506) and social_facility (#1295) as societal amenities - with a light yellow background.

I would also like to add arts_centre, since this is sometimes similar to community_centre, but I'm not sure if this would be accepted - what do you think about it? We don't have a clean, generic solution for lot of "campuses" and social services, so I prefer to make smaller steps where this seems quite consistent rather than try to solve as much as it's possible.

amenity=social_facility
Before

After

amenity=community_centre
Before

After

[polarbearing]

Looks fine for me. Do I understand correctly that we only add the fill, and leave the label as it is?
That means not scaling with area size. Which is probably fine, since these campuses tend to be compact in comparison to large schools/universities.

And yes let's continue in small steps and not throw in all ideas at once. I have more ideas, also.

[kocio-pl]

Yes, we have no idea what to do with scaling when we show the icon. If we knew, we would have school icons set already (see #2361 (comment)).