The over-the-air newline format has been changed to LF always, for
simplicity. We might have used CR instead but LF works, and is the
newline format normally used on Unix (in files and stdio, except for raw
terminals).
Use a new Duration type, which is used throughout the BLE stack for
durations. The resolutions are sometimes different (connection
parameters have half the resolution) but overall it should improve the
ease of use of this type.
This commit also provides a default advertisement interval that is
recommended by Apple (which I think is as good as any recommendation).
This might help to speed up discovery by Apple (and Android?) phones.
