Draft: Separate metadata and visualisation/download into left/right columns

This is a draft attempt for discussion to address #39, and partially address #48 (closed).

By removing the embedded neuroglancer viewer, this fixies #39, and means that the page has a layout where dataset information and metadata are on the left, and dataset visualisation and download are on the right. This helps with making the citation requirement more obvious, because to do any data download or visualisation you have to go to the right hand column, which is where the citation requirements are.

I'm not sure if this is the best solution? But an idea to start with.