Synchronized the process of loading and parsing YAML databases.
Provides more robust parse warnings/errors.
Added Header checks to validate database versions.
Adjusted root keys to a standard name of Body.
Adjusted inter-server storages, achievements, and attendance to follow the new format.
Fixes#3483
Thanks to @Lemongrass3110!
* Alphabetically sorted includes.
* Updated copyright and license text to match across all files.
* Removed pragma once define in header files in lieu of ifdef guards.
