20 Hz of RC_CHANNELS makes the RC calibration in QGC a more pleasant
thing.

look for alternate topic list at
/fs/microsd/etc/logging/logger_topics.txt
on and off commands have the same effect as arm/disarm

Previously, if no time was set, sdlog2 created a folder like sess001,
sess002 for every logfile. The logfiles would then always be named
log001.px4log and their numbering would not actually increase.

This is now fixed and a new folder is only created per boot.

Change prefix construction to allow correct building of scope tag in parameters.xml when building out-of-tree (#4781)

Fixes issue #4767

Namely the following output after Ctrl-C:
Invalid command: muorb
type 'help' for a list of commands

Before the output looked like this:
pxh> logger statusINFO  [logger]   Running
INFO  [logger]   Wrote 0.13 MiB (avg  0.72 KiB/s)
INFO  [logger]   Since last status: dropouts: 0 (max len: 0.000 s), max used buffer: 7176 / 12288 B

remove unnecessary replay fields

This reverts commit a9a0759d.

This only removes one printfs, nothing fancy.

Sensors app: Use two parameters to convert battery current and voltage to make configuring custom frames easier

px4_task_exit doesn't seem to be available for NuttX, so it had no
effect and broke the init because the return values of the tasks were
wrong.