Sticky footer updates for b57

[danicahelb]

• the footer is too tall, please shrink the height of the footer

• it is not completely clear, in the footer, why all those icons are there. The relevance of the icons is to indicate that ClinEpiDB is part of a larger family of data resources. for a naive user, i am not sure they will understand. i wonder if the footer should make that more obvious.