Improve Timing interface.
Improve Timing interface.

This removes the (sketchy) checkpoint timing, and adds an overload
which allows you to use the thunk result in the log message.

drostron/quasar,slamdata/slamengine,drostron/quasar,quasar-analytics/quasar,quasar-analytics/quasar,slamdata/quasar,quasar-analytics/quasar,jedesah/Quasar,slamdata/slamengine,slamdata/slamengine,quasar-analytics/quasar,jedesah/Quasar,djspiewak/quasar,drostron/quasar,jedesah/Quasar,jedesah/Quasar,drostron/quasar