This allows a simple-to-use bootloader update mechanism to switch from
fmu-v2 to fmu-v3 target that has more flash.

Added an imu heater driver, formatted whitespace, standardized comments, and added doxy documentation.

Edit the init.d-posix files to set MAV_TYPE script variables, and alphabetize lists in a few places.

Set parameters directly rather than script variables in VTOL airframe config files and alphabetize lists.

Starting with cmake version 3.12 the cmake -E copy_directory
command fails if the source directory does not exist. This results
in a build failure. This fix creates the source directory before
the copy which does not harm if the source directory exists.

Closes: #10368

   On FW with a px4io bin file, but not a px4io do not error

   Use tune control and have all paths in rcS indicate tunes

such that fractions of a second are configurable

 * tested on SPI (px4fmu-v4pro)
 * WIP I2C support

 - fix ocpoc line endings

    NXPhlite does not have a companion link. So start
    Mavlink on ttyS4 and ttyACM only.

Directly set parameters in airframe config files rather than setting script variables and move the param set lines into  logic blocks, and alphabetize and tidy up param set lists.

* jenkins: decrease VTOL mission alt and FW mission use simple land wps
* startup: decrease min airspeed scaling factor for landing
* jenkins: FW mission include loiter_to_alt cmd

The -P argument seems not to be supported on OSX

  On a FMU without a px4io (FMUv4, NXPhlite etc), this code should
  not be run.

   Since the only device on the bus is the barro, int or ext does
   not apply. This will be fixed on the rev > RC15.
   This defines an alias that can be used to condition the buss logic
   connection logic px4_i2c_bus_external to return external.

Use './Tools/run-shellcheck.sh ROMFS/px4fmu_common' to run it.

This info is on the dev-guide now