Support encoding options on chained batch

[vweevers]

While we support passing options to chainedBatch.write(), encoding-down encodes keys and values before write() is called. We can keep that as-is, but should allow encoding options on chainedBatch.put() and chainedBatch.del().

E.g.: chainedBatch.put(key, value, options).

To be added to:

• abstract-leveldown: 7.0.0
• encoding-down: 7.0.0
• levelup: 5.0.0
• level (just documentation): 7.0.0

[liximomo]

Really need this