Plane: switch to an array for stream rates

this saves a couple of hundred bytes of flash.
RC_Channel: added secondary elevator support
Plane: added secondary elevator support
After Plane: cleanup driver declaration 4d9a74d, HIL_MODE_ATTITUDE with MAG_ENABLE=1 set results in continuous reboot/APM crash.  Added define for AP_COMPASS_HIL when HIL_MODE_ATTITUDE is enabled.
Plane: Implement issue 80: counterclockwise loiter

- libraries/AP_Common/AP_Common.h: Use bit 2 of Location.options to store
  loiter direction
- ArduPlane/defines.h: New bitmask MASK_OPTIONS_LOITER_DIRECTION for struct
  Location bit 2
- ArduPlane/ArduPlane.pde: New variable loiter_direction
- ArduPlane/GCS_Mavlink.pde: For mavlink loiter-commands use sign of param3 to
  detemine direction. Set Location.option flag accordingly
- ArduPlane/commands.pde: Make sure loiter-directions get saved into EEPROM
  correctly
- ArduPlane/commands_logic.pde: Set loiter_direction on all loiter-actions
  as well as RTL/instant loiter
- ArduPlane/navigation.pde: Yield loiter_direction in update_loiter
Plane: fixed bit combination

bitwise, not arithmetic
Mission planner moved notice
autotest: added some hints to sim_arduplane.sh
autotest: expand the comment a bit more
AP_InertialSensor: always sample at 200Hz in MPU6000

this changes the sampling to 200Hz regardless of requested rate, and
it is downsampled inside num_samples_available() using a shift. This
gives better noise resistance in ArduPlane.

This patch also makes it possible to update the filter frequency while
running, which is very useful for bench testing with a vibration
source
AP_InertialSensor: removed unused new_data_available() and temperature() APIs
AP_InertialSensor: added filter frequency support to PX4 driver
Fixed cosmetic typo in user display message

Corrected "it's" to "its". Just one of those grammar things that drives me crazy ;-)
AP_HAL: added run_debug_shell() hal.util method
HAL_PX4: added run_debug_shell() implementation for PX4
Plane: added shell command for px4

used to launch nsh for PX4IO firmware upgrades
Copter: removed use of ins.temperature()
Rover: major restructuring

this removes a lot of the old arduplane code, and renames a lot of
variables.

This will need a lot more testing and fixup before being usable
Rover: rename Attitude.pde to Steering.pde
Rover: added filter to auto steering, and fixed throttle pid