Feature - Add "Approved" Quality Code to Unsigned bit

[msweier]

It would be nice to have an "Approved" quality code that would denote that the data has gone through a human QA/QC process and is unlikely to change. Then we can differentiate from preliminary and approved.

[adamkorynta]

Make sure not to clash with original approved "A": https://github.com/USACE-WaterManagement/CWMS-Data-Quality/blob/master/src/timeseries/Quality.ts#L503

[rma-psmorris]

Consider using a combination of bits to represent a broader set of quality codes as opposed to defining independent singular bits as on / off.

[rma-psmorris]

Bits	Value	Meaning
0000	0	Unknown
0001	1	Accepted
0010	2	Reserved 1
0011	3	Reserved 2
...	...	...
1111	15	Reserved