Make Scan less like Level DB Iterator and more like Scan api

[miketheprogrammer]

Currently Scan only exposes a few methods, and under the hood abtracts alot of other things away. Like lastEvaluatedKey, moreDataToCome.

Scan currently just uses next, and determines if there is more data to come and then creates a new scan with relevant parameters. While this is great for most javascript developers and especially users that favor the levelup style, it sacrifices a bit of control that bangdb offers.