Fix for JSONPointer, for stleary/JSON-Java#233

[erosb]

No description provided.

[stleary]

What problem does this code solve?
Users should have the option of performing a JSONObject or JSONArray JSONPointer query without an exception being thrown when the string does not match an item in the document. The optQuery() methods support this option.

Changes to the API?
Yes. 2 new public methods are defined:

• Object JSONObject.optQuery(String)
• Object JSONArray.optQuery(String)

Does it break the unit tests?
No, but new unit tests will be added after this commit. Those tests will fail unless this code is committed. See stleary/JSON-Java-unit-test#48.

Will this require a new release?
No, but this will be rolled into the next release, which is expected in May-June 2016 timeframe.

Should the documentation be updated?
Yes. The JavaDoc should be updated.