Zipper function - archive browser

[zxch91]

Things to do:

• [x] Make the archive-browser work on your laptop.
• [x] Make a zipper branch in the repo
• [x] Add a button that triggers zipper javascript function. use the code attached and point to dap.ceda.ac.uk urls for a couple of random files.
• [x] Make the button only appear if the number of files is less than 10,000 and less than 1GB.
• [x] Use fbi-core to get the proper list of files.
• [x] #122
• [ ] Test on other data
• [ ] talk about deployment.