Improve input column descriptions in manual

[hugomflavio]

From Simon Dedman:

One thing I think could be really helpful would be to explain what each column IS, so that one understands what they're looking for, potentially from a mix of different columns.
You have this for most of them, but it might be good to be more explicit with CodeSpace (in Detections; "Code.space" in biometrics, concerningly), explaining that the original Transmitter string may typically consists of the CodeSpace ("A69-1008") followed by the Signal ("A69-1008-12345"). You could go further by suggesting relevant code tips for the users, e.g.

      dplyr::mutate(Timestamp = as.POSIXct(Date.and.Time..UTC.,
                                           format = "%Y-%m-%d %H:%M:%S",
                                           tz = "UTC"),  # "America/New_York"
                    Signal = as.numeric(stringr::str_sub(string = Transmitter,
                                                           start = 10,
                                                           end = -1)),
                    CodeSpace = stringr::str_sub(string = Transmitter,
                                                 start = 1,
                                                 end = 8),
                    Receiver = as.numeric(stringr::str_sub(string = Receiver,
                                                start = 6,
                                                end = -1))

It would be good to have explanations for detections$Sensor.Value & Sensor.Unit.