Show recent validator stats

[orogvany]

As time goes on, the delegates 'rate' column becomes meaningless.

It would be ideal if this allowed validators/voters to see recent statistics, so a validator can tell when they are failing forges, and voters can see recent pool rates.

We should show forging rate over last ~week, either replacing or adding an additional column

[semuxgo]

This a nice feature to have. Let's move it to v1.6.0