JSONPath support for merging

[EliteMasterEric]

trafficstars

This is similar to #64.

JSONPath support would allow similar flexibility in modifying keys of deeply nested and intricate structures as XPath. It would allow for modifying, adding, and removing elements without requiring the developers to maintain the order of items in arrays.

However, the major obstacle to this is that there is no implementation of the jsonpath algorithm for Haxe, that I know of.

[EliteMasterEric]

https://jsonpatch.com/