* Refactor and document the Watchdog driver to make it more readable.
Fix the configuration of the behaviours configuration that was not properly implemented (but it didn't cause any side effect since the correct value was eventually set in NRF_WDT->CONFIG).
Fix the wrong interpretation of the reset reasons caused by implicit conversions of int to bool.
Don't use relative imports like `../foo.h` as those depend on the
relative position of both files. Rather than that use imports relative
to the `src` directory, which explicitly is part of the include
directories.
