Add a set of "withParser(...)" and "withGenerator(...)" methods in TokenStreamFactory for auto-close

[cowtowncoder]

Currently createParser() and createGenerator() methods require caller to take care of closing of parser/generator, allowing possible loss of things like file handles and URL connections (see #803 f.ex)

But it would be easy to add a complementary set of methods that would be similar to matching "createXxx()" methods but take an additional closure, callback to which parser/generator would be passed and which could return a value (like object bound with readValue()).

Although we could technically add this in 2.x (since Java 8 is now the baseline with 2.14), it seems that for backwards-compatibility reasons this is better for 3.x when jackson-databind can make good use of the new functionality -- especially as JacksonException becomes unchecked.

[cowtowncoder]

Thinking bit more about this, I don't think there is much value for general usage -- it would only help with #803, but with many new methods, complexity.

So closing for now; may be re-opened if there are good arguments for re-considering.