Also clean up unused PRS1 channels and fix a regression from
9a25647c that broke unintentional leak calculation for CPAP/APAP.
Also add PRS1PressureAverageEvent to F0V4 list of supported events.
Right now this results in slightly confusing graphs, since sometimes
the IPAP/EPAP data for a machine is primarily reported by its settings
events, and for other machines by its statistics events. Also, the
"average" pressure on F0 looks like it might be effectivley EPAP in
single-pressure mode rather than the true average in bi-level mode.
Once we decide on the best presentation, we can either update the importer
or the display to show the most helpful channels for a given session.
This one's slice 8 is shorter than anything else we've seen before!
Also add support for a new slice type and noted possible values
for other data, including a possible lead on the CPAP mode.
Remarkably, this resulted in nearly no changes to the test output.
Only one session with 0 duration had its start/end times reset to 0,
since it will no longer get imported.
This has already exposed many limitations, and possibly some memory trampling. Before this will work as
a true regression test, we'll need to address both of those, so that this produces reliable, reproducible
output.
