doc(doc/time):Document time tracking setup

Also:

- Add TODO item to use `chrony` instead of `ntpsec`

- Modify `/doc/setup/README.org` to note need to disable bluetooth

- Modify `/doc/location/README.org` to note possible need to modify
`gpsd` configuration file again in order to provide ~pps~ signal to a
time tracking program such as ~ntpsec~.