px4io: split io_handle_battery() out from io_handle_status()

ready to add vservo and rssi
uORB: added new servorail_status object

used for VSERVO and RSSI on FMUv2
px4io: added monitoring of vservo and vrssi

publish via servorail_status ORB topic
added error_count field to sensor report structures
perf: added perf_event_count() method

this allows drivers to get an event_count from a perf counter
Merge branch 'master' of github.com:PX4/Firmware into status_monitoring
drivers: report error_count in drivers where possible
Merge branch 'master' of github.com:PX4/Firmware into status_monitoring
RC3 usually used as Throttle, but trim was set to 1500 by default.
It should be 1000 by default.
There were unintialized variables.
(control mode was not updated)

Also, new flags (xy_valid etc) were considered.
Airframe No. 21. 22 have been added.
That is for general ESC with PX4IO (frame geometry defined)
Update sensor_params.c

Not necessarily modify this on initial.
Merge pull request #426 from limhyon/master

PX4Flow, and several tiny things enhanced.
Merged status changes
State machine fixes for HIL
Robustified flight close to waypoints
px4io: make "too high rate" warning consistent with real behavor
Merge pull request #442 from PX4/px4io_rate_fix

px4io: make "too high rate" warning consistent with real behavor
Added useful default gains
Fixed turn radius return value