Copy v3 --> v4
Rename v3 --> v4 within json
Remove worksheets (just have an array of cells)
Make indent level be consistent
Fix a few small spacing things
Make cell content key uniform

Change code cell and text cell inputs to all be called "source"
Remove notebook name from metadata
Move language key from code cells to top-level notebook metadata
Add kernel info to top-level notebook metadata in some form
Add state for auto-scroll
Replace 'worksheet' with 'notebook'
Conform better to JSON schema version 3
Misc style changes to descriptions
Fix JSON syntax errors
Add signature to notebook metadata
Add separate raw cell type, fix "source" property of cells
Fix a few errors
Add skeleton for different output types
Flesh out output types
Fix errors