update TERRA BETYdb landing page

[ghost]

on https://terraref.ncsa.illinois.edu/bety/

• [x] change the default text in the search box from "EX: Panicum Nitrogen" to "EX: Sorghum MAC" [will take effect when a new release is pushed to the Terra Ref site]
• [x] remove Model I/O from menu - this refers to EBI data [will take effect when a new release is pushed to the Terra Ref site]
• [x] fix footer image display (remove sorghum image if that is easiest)
• [x] make sure sponsor logos appear nicely
• [x] Change title to "TERRA REF Phenotype Database" (removing BETYdb) [see note below]

[gsrohde]

I changed "Phenotype Database" to "TERRA REF Phenotype Database" in the site identification markup but I didn't remove the BETYdb. This is the name we use to refer to the Rails Web application and the database schema used by both the EBI and the TERRA REF databases. I was partly following the model of David's Gist here https://gist.github.com/dlebauer/cfd4bb6de70d8ae75bec6804d8c3b16a/revisions where he changed "TERRA REF BETYdb PhenotypingDatabase" to "BETYdb Phenotype Database". The BETYdb name is used other places in the site (twice in the footer) and I wasn't prepared to drop all references to BETYdb willy-nilly.

[gsrohde]

Keeping this open pending further improvement to sponsor logos.

[gsrohde]

Logos improved. Closing.