JSON block format

Dn-FT JSON block format version 1.1

must always be backwards compatible using a never remove, only add strategy

{
	// Device mixing offsets, described in centibels. too late to change to millibels.
	// range is +- 12 db.
	"apu1-offset": 0,
	"apu2-offset": 0,
	"fds-offset": 0,
	"mmc5-offset": 0,
	"n163-offset": 0,
	"s5b-offset": 0,
	"vrc6-offset": 0,
	"vrc7-offset": 0
}