Add initial support for the Oceans S1.
This expands a bit on the generic functions for the field-cache code,
and uses that to then add a fairly minimal Oceans S1 downloader.
And while it's minimal, it downloads about everything the S1 offers,
which is mainly just depth and temperature.
There are a few fields that it currently doesn't use, notably the
events and NDL information that the dive computer presumably reports in
the auxiliary data that comes in the sample, but without documentation
and more testing I'm not comfortable parsing that.
There's also some "current dive computer state" that isn't imported,
like the battery status. I know how to read it, but it's not per-dive
data that could be added as extra fields: it's literally just the
current dive computer battery state at the time of the download.
The Oceans team said they'll provide more information about the
download, so this might be expanded in the future, but it seems fairly
usable even in this form.
Thanks to Dhaval Giani for sending me his Oceans S1 as a loaner, and to
Seth Garrison for doing the initial BLE packet dumps that made me think
it was fairly easily doable.
* Oceans-S1:
Oceans S1: polish up the downloading logic for usability
Oceans S1: actually download all dives and parse them
Oceans S1: fill out core download protocol details
Oceans S1: start filling in protocol details
Oceans S1: start documenting the download format and first packets
Add skeleton for Oceans S1 downloader
Add generic dc_field_get() helper
6935fe717a