api papi: add alias for timestamp(datetime)/timedelta

api papi: add alias for timestamp(datetime)/timedelta

Now that we have support for f64:
- create explicit types for timestamp(datetime)/timedelta
- update log_details to use timestamp and remove redundant string representation.
  If you need the string representation, in python do str(timestamp).
  If you prefer the raw f64 value, the client can pass in the
  _no_type_conversion option.

Type: feature

Change-Id: I547b5fa7122d2afa12628b7db0192c23babbbae8
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>