Mark3 RTOS Source

- Adding examples for mark3c APIs
- Adding Arena unit test

Adding documentation to the cm3 example code describing how to build code with vendor libs and linker scripts

Refactoring kernel headers to support the mark3c, C-language binding lib.

Add code in mark3c to automagically generate the size of kernel objects when declared in C. This should allow mark3c to run on all supported targets.

Beginnings of Mark3C library -- Mark3 with C-language bindings. Preliminary work supports AVR only, needs further development for MSP/ARM support.

Adding missing "stddef.h" define for arduino port, necessary for autoalloc support.

- Adding placement-new operator for all kernel object types, allowing for them to be dynamically allocated from user-created heaps, without overriding global new/free
- Added helper methods to AutoAlloc class for allocating/initializing kernel objects (wrapper functions for placement-new)

-Adding compile-time error macro to demos that only build with KERNEL_USE_IDLE_FUNC
-Prevent ARM targets from building with KERNEL_USE_IDLE_FUNC by default, but set as default for AVR and MSP430

Fixing unit tests for tick-based timer compatibility.

-Updating manual and readme to reflect new configuration scripts
-Updating lab code to use correct stack sizes as part of thread init.