Started migrating to C and Unity

From what I've seen so far C++ complicates things
more than it helps you out. I want to work with
Grenning's book so and try his ideas so I'm
switching to C and to using Unity for unit test
framework.

It should be possible to simplify the module
makefiles somewhat, give it a thought until
next time...
Minor touchup

* Deactivated "-Wall" for unit test compilation because
Unity has warnings in it

* Removed unnecessary make definitions
Removed "gtest" and "old", not needed anymore

Google Test has been replaced by Unity

"old" is from back when we were aiming to deploy on
a TS7400. Not useful anymore.
Removed file extension macros

They were actually making the code harder to read
Made 'motor' turn on the LED when started

* Made 'motor' turn on the LED when started

* Changed led dummy test to always pass

* Made test runner compilation output the triggering
dependency

* Improved "unity.mk"'s compilation output
Improved 'motor' test

LED state is now better represented
Improved 'motor' test

LED state is now better represented
'motor' now switches off LED when stopped

(Merge because of previous 'commit --amend' operation
Conflicts:
	src/motor/test/motor_tests.c)
Sanity-check for build 'VARIANT'
Improved build sanity-check

'clean' build does not require 'VARIANT'
Added simple "build.sh" that builds everything
Clarified "unity/all_unit_tests_command.mk"

* Added file description
* Added use of 'TEST_SUITE_SUFFIX' for test suite names
Added some clarifications to "makefile"
Added "doc" directory

* Added screenshot for minicom settings for buspirate
Added UML for 'SabretoothVehicleControl'

* Removed "minicom_settings_for_buspirate.png" because it
  belongs on the wiki

* Added UML for 'SabretoothVehicleControl'
File rename

"vehicle_control.class.violet" ->
"sabretooth_vehicle_control.class.violet"