Add an indication when chains don't have a week's worth of data.

[brson]

Pair this with #73

As it is, we claim to calculate TPS with a week of data, but for various reasons wipe the db or single chains with some frequency.

Like the red exclamation for failing chains, we could add another indicator for chains that haven't accumulated a full data set. Maybe a clock, with a hover tip, and a link to the 'log' page.