Add minimal profiling for stats

This shows just how much time we spend on the database query and later
processing.

I was hoping to be able to skip the sort step if the data is already sorted and
found out that it frequently isn't, even if the user hasn't touched the
database. The data appears to arrive out of order from Tesla.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix incorrect week number calculation (for US)

With this weeks start on Sunday and the correct "first day of week" is used to
visualize the data.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Better labels for the weekly stats

And change the title of the page.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add tooltips for weekly chart

And remove unused code from the tooltip for daily chart.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>