Add new method for ObjectReader to bind from JSON Pointer position

[islanderman]

Implement #820

Outline

Add two APIs as part of the change:

public ObjectReader at(final JsonPointer pointer)
public ObjectReader at(final String value)

Implementation

Add filter to be consider for JsonParser. Default value to be null as filter not considered.

private TokenFilter _filter;

---

Add unit test cases for the change. All unit test cases are passing.

[cowtowncoder]

Looks good to me, thank you for contributing this!

The only change that will be needed is to make _filter final, to keep ObjectReader immutable; that is how all current configurability works. It is bit cumbersome to support (needing changes to constructors), but it is the approach taken to ensure 100% thread-safety via immutability.

[islanderman]

Thanks for the comment. I also added more test cases and followed your naming convention.

[cowtowncoder]

Most excellent, thank you for implementing the feature!