Double parser merge to master

[pjfanning]

Relates to #749

[pjfanning]

@cowtowncoder this is WIP and miles away from being complete - master and v2.14 are so different that most of the code in this PR has been neutered to get the code to compile. I'll need help to work out how features are enabled in master.

For instance, how do you create a JsonParser with a JsonReadFeature enabled?

TokenStreamFactory has public abstract JsonParser createParser(ObjectReadContext readCtxt, InputStream in) but ObjectStreamFactory only seems to have an empty implementation (ie ObjectReadContext.empty()). I can't find another class that implements ObjectReadContext.

[cowtowncoder]

@pjfanning ObjectReadContext is typically passed by databind where context (DeserializationContext for parser, and similarly SerializerProvider for output, ObjectWriteContext) is implemented. I have been thinking of whether to implement one for testing purposes in jackson-core.

However: right now you can construct a JsonFactory with suitable defaults

JsonParser p = JsonParser.builder()
   .enable(JsonReadFeature.FEATURE)
   .build();

which is probably what tests should use.

Now: I'd be perfectly happy to convert these from 2.14 to master as I know how to modify changes -- all I'd need is the initial scaffolding. This is why I asked for a subset, to get first tricky (but small) part merged. After this, rest of the code is fine.
I actually prefer single PR for 2.14 over having separate full PRs for 2.14 and master since latter can just defer conflicts. Although if you want to go over conflict resolution that's fine too. It's just that I often end up doing those anyway so that's fine :)

[pjfanning]

@cowtowncoder thanks - I can use this just to keep track of the merge issues and the changes that have been made to get master working - so it doesn't have to be merged

[cowtowncoder]

I suspect this can also be closed now that things are merged to master?