Revert "AP_NavEKF : Reduce ripple in estimates that can cause copter motor 'pulsing'"

This reverts commit 13df6fb1c9f1c42ddda3250fec3486212213463c.

This patch was a result of an incorrect merge of the optflow branch
into master. It reintroduced the bug fixed by this commit:

  AP_NavEKF : Fix bug in reset of GPS glitch offset
  8aa267f75fb1e7161505974b4ac2f7eef95a6cd1
HAL_Linux: run IO processes when we do a stop_clock()

this has the effect of allowing logging to progress in Replay where we
are running at much more than realtime speeds
Replay: generate dataflash logs in Replay

this allows the calculated EKF flight path to be compared with
different parameters by using replay
Copter: remove OF_Loiter from FLTMODE param descriptions

Also remove OF_Loiter reference in comments
No functional change
Copter: remove OF_Loiter PIDs and tuning
OptFlow: remove ADNS3080 image grabber example
Copter: move update_optflow to sensors.pde

No functional change
Copter: optflow instantiation format change

No functional change
Copter: add OPTFLOW to default logging
Copter: optflow logging minor format change
Copter: send optflow health in extended status
Plane: send optflow health in extended status
GCS_MAVLink: add OPTICAL_FLOW to ap_message enum
Copter: send OPTICAL_FLOW msg to GCS
Plane: send OPTICAL_FLOW msg to GCS
AP_Compass: Made some suggestions regarding, performance, interface and docu

Signed-off-by: Daniel Frenzel <dgdanielf@gmail.com>