Gets whether or not the header should be copied from a default source.
If this is true, if a default
FileConfiguration is passed to
FileConfiguration#setDefaults(org.bukkit.configuration.Configuration)then upon saving it will use the header from that config, instead of
the one provided here.
If no default is set on the configuration, or the default is not of
type FileConfiguration, or that config has no header (
#header()returns null) then the header specified in this configuration will be
used.
Defaults to true.