* Thread-safe.
* Provides getter/setter functions for the data types used by nxdumptool's configuration.
* Each setter function writes the modified JSON configuration back to the SD card.
* Configuration is validated on interface initialization. If validation fails, a default JSON template is loaded from the application's RomFS and written back to the SD card.
Other changes:
* Implement directory creation.
* Moved more preprocessor definitions to defines.h.
* Replaced strtok() calls throughout the code with strtok_r() to guarantee thread-safety.
