Defer I2C bus resets for the first couple of retries to avoid transient slave errors causing massive retry spam.
Increase the number of I2C retries.
Rename ::start to ::start_cycle to avoid confusion with the other start function.

Only enable I2C retries on operations that have no side-effects.
Re-order register page variables to match the order registers are defined in the protocol header.
Disarm IO at driver startup time.
appconfig: disable mathlib and associated examples on APM

these are far too large (777 kbyte) and we can't fit them with the
ArduCopter flight code
px4io: make uploader more reliable

avoid seeks, lower verify recv size and removed cruft
px4fmu: APPS_BINDIR has been renamed to FS_BINFS
px4io: setup for debugging on ttyS1
px4io: added isr_debug()

this is useful for debugging px4io internals
px4io: bit more verbose debug output
px4io: don't spam console on FMU timeouts
headers: fixed comment on clock timing
px4io: added a "px4io debug N" command

this allows the debug level in px4io to be controlled from nsh
on the FMU
px4io: added PWM_IO_SET_FEATURES ioctl

useful for controlling manual override behaviour
px4io: reset the I2C bus if dead for 0.1 seconds
px4io: show more flags in tick output
ms5611: still need _retries 0

using non-zero _retries leads to altitude errors