Deprecate `URL`-taking factory method of `JsonFactory`

[cowtowncoder]

(follow-up to #803 )

Due to complexity of trying to manage JDK provided URLConnectionStream (created via JsonFactory.createParser(URL)), existing usage has issues: see #803 (and #1461). But since this functionality is, in many ways, "extra", we should probably get rid of it, instead of adding more work-arounds.

For backwards-compatibility we cannot really remove this method from 2.x but can deprecate it.
We can remove it from 3.0.0, although timing can be an issue at this point.

Note, too, that similar changes are needed in jackson-databind to align with changes here.

[cowtowncoder]

cc @sdeleuze