Copter: add short delay to arming to allow RC input

The short delay gives time for the RC inputs to be processed which
removes the chance of a false-positive on the "late frame" radio check.
A false positive could lead to an immediate disarm right after arming.
Copter: land check gets overall throttle and rotation rate check

add check that overall throttle level is below the non-takeoff throttle
instead of just checking that it's motors have hit their lower limits
because low limits can also be caused by high yaw rotation requests.
Absolute climb rate requirement reduced to 30cm/s
Copter: pre-arm consistency check of gyros
Cotper: AC3.2-rc7 release notes
Copter: version to AC3.2-rc7
Copter: increase EKF_CHECK_THRESH default to 0.8

Also remove unused #define related to inertial nav check (now removed)
Copter: reduce alt hold defaults

Throttle Rate P to 5.0 (was 6.0)
Throttle Accel P to 0.5 (was 0.75)
Throttle Accel I to 1.0 (was 1.5)
TradHeli: update AttControl params to match multicopters
DataFlash: allow use of a smaller writebuf for PX4v1

this fixes logging on PX4v1
Copter: send extended status to GCS only after initialisation
Copter: never send unhealthy terrain status

Copter does not yet rely on the terrain data (it's for informational
purposes only) so we will temporarily disable the failure flags to the
GCS to avoid support calls
AP_NavEKF : Clean up time stamps

Time stamps are now explicitly initialised to the current IMU time to avoid unwanted activation of timeout logic on filter start and various calls to the hal.scheduler->millis() object have been consolidated.
AP_NavEKF : Reduce ripple in estimates that can cause copter motor 'pulsing'

This patch reduces the level of 5Hz and 10Hz 'pulsing' heard in motors due to GPS and altimeter fusion which cause a small 5Hz and 10Hz ripple on the output under some conditions. Attitude, velocity and position state corrections from GPS, altimeter and magnetometer measurements are applied incrementally in the interval from receiving the measurement to the predicted time of receipt of the next measurement. Averaging of attitude state corrections is not performed during periods of rapid rotation.
Copter: AC3.2-rc8 release notes
Copter: version to AC3.2-rc8
HAL_PX4: fixed dirty_mask calculation in FRAM storage

this could lead to a number of bytes on 512 byte boundaries not being
written when changed in ram, so they would revert on next boot
HAL_VRBRAIN: fixed storage bug in VRBRAIN too
Copter: AC3.2-rc9 release notes
Copter: version to AC3.2-rc9
Copter: THR_ACCEL_IMAX param range increased