Time units

[LPardue]

Its still ambiguous what units the logged time field uses. Issue spun off from the other clock updates in the PR below

          I don't understand this bit. If I have a float64 field, and I decide to use it to log "1.5" to mean one and a half seconds, but the logger tool thinks I meant one and a half milliseconds, then there's an interop issue. So I think we need to pick one form of "units of x with fractional Y", or add a field to articulate the concrete units and precision.

Originally posted by @LPardue in #433 (comment)