The Coindesk API doesn't have data going all the way back. But since history
isn't changing, we can simply put in known prices.
Also, extend the CDPR cells to have four digits instead of just two.
* Full screen ("alt framebuffer").
* Rounded borders.
* Spinner that starts during a refresh.
* Colored table headers.
* Table header have bottom border.
Instead of pre-allocating the grid and using tricky indexing to fill in
the cells, just fully regenerate it. But do it columnwise first, and
then transpose it.
