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
AP_Relay: added RELAY_DEFAULT parameter

this is useful when using a Pixhawk with an external relay, as it
allows you to cope with the pullup on the PWM pins
Copter: minor ReleaseNotes format change

This also helps to kick off the build of AC3.2-rc7
Frame_parameters: Updated Iris with 3 Position Mode Switch