Remove old campaign fallback.

This is left over from when we launched the dynamic homepage from the
old hardcoded one.
Load sponsor images for homepage from partner taxonomy.
Export partner homepage image style.
Fix display of sponsors when wrapping to multiple lines.
Scale down logo size on smaller mobile screens.
Clean up sponsors field and export feature.
Get correct term name.
Merge pull request #3202 from DFurnes/homepage-sponsor-admin

Homepage sponsor admin