Application configuration option documentation license change

[Sebastian Huber]

Hello,

for your information, I carried out the license change of the 
application configuration options documentation. They are now under a 
dual CC-BY-SA-4.0 or BSD-2-Clause license.

https://git.rtems.org/sebh/rtems-qual.git/commit/?id=c116767b19e109f007d683e477481af67d603816

This allows generation of documentation sources under CC-BY-SA-4.0 
license and Doxygen markup under BSD-2-Clause license.

I work currently on a generation of the Doxygen markup. This allows to 
easily reference configuration options in the Doxygen documentation. For 
example, this can be used to improve documentation for configuration 
defined data structures such as:

/**
  * @brief Registered schedulers.
  *
  * Application provided via <rtems/confdefs.h>.
  *
  * @see _Scheduler_Count.
  */
extern const Scheduler_Control _Scheduler_Table[];