Option to download dataset (or search results) as a csv file

[bdeadman]

Ability to download the dataset as a csv file is displayed as "coming soon". This could be a useful entry point for new scientists to start using ORD as a data source.

A csv with all fields may have excessive columns, so it may be helpful to have an option to get a csv of the changing fields, and an associated .pbtxt file of only the first reaction to provide the meta data including static fields.

[bdeadman]

Should return a .csv file after constant columns have been removed. Could maybe be supplemented with a .pbtxt for first reaction to show the rest of the data.