Calculate / generate / show Personal Bests and PRs for distance and time

[mbifulco]

For any given user, once some data is calculated, pistola should be able to display:

• best 1mi, 10mi, 25mi, 50mi effort (etc, depending on whether running or riding)
• best 1min, 10min, etc effort
• best distance in a 7-day and 30-day period
• time spent on each activity in a 7-day and 30-day period

[mbifulco]

It would be amazing to see a progression of each PR over time, and which activity landed each best