Exporting

As of USASEF we noted the need to be able to export data sets as 
1) Individual files (current standard)
2) A Single concatenated file

Now, when you click the export button a modal appears that asks which you would like to do. Individual files export as a zip, concatenated exports as a csv.

Also fixed styling of a few buttons on the experiment show page. 

TESTERS: Please try exporting a project with multiple data sets both ways and verify that this works.