Add instructions on how to download sample data

[jonmatthis]

Here's two pieces of sample data -

• From the NEUron's talk - https://drive.google.com/drive/u/1/folders/15gIxDuZBuCEDKnkBks6cp6HUBHSvI7Mx

  • more of a 'science' focus because there's a one-foot stand section and an ipynb to pull the data in and do a very basic BOS vs COM analysis.
  • Unfortunately, the recording itself isn't great quality, so another TODO would be to adapt that ipynb to work with this data from my class: https://www.dropbox.com/sh/0oiy59k0q2a5n51/AACDxPsRiDZ0kY37sACmAmtba?dl=0

• Here's an older one that's more animation focused - there's a wee bit of dancing and the hands are tracked well:
  https://www.dropbox.com/sh/4koegtwlxwz6lvn/AADG_rJxxf_q8diougEElZY1a?dl=0

To do:

• Download the sessions and process them with the GUI so all the right file names exist (esp for the dancing one, because it was made with teh pre-alpha)
• Clear out files that don't need to be there(but keep whatever needs to be there for the blend files to keep working, i.e. the Synced Videos folder?)
• Host them on a friendly public place (e.g. figshare)
• Add instructions on how to download them and a brief walk through of the contents (focus on the alpha files/filenames)
• Update the 'process synced videos' guide with tips on how to process those sessions (for folks without their own videos).
• Maybe also - we could use the pre-alpha session as an example of 'how to re-process a pre-alpha session with the alpha GUI?