Add Builder pattern for creating configured Stream factories (nee JsonFactory)

[cowtowncoder]

(and make factories truly immutable)
(note: for background see #3)

Although actual mutability of JsonFactory (and subtypes) has not been a significant source of issues (compared to ObjectMapper), same theoretical issue exists, and ideally factories would be immutable to guarantee that users can not try to apply changes that either do not take effect, or even cause problems.

Given that parser/generator features can already be defined at higher level (and passed through API with 2.x, with some improvements planned for 3.x) this is probably not a huge change for JSON factory. There may be more questions on other formats, but even there most changes can already be applied via FormatSchema (for CSV for example).

[cowtowncoder]

Note: will require removal of some configuration functionality, and probably addition of some extension points. Still, not primarily considered functionality removal (although technically we will remove ability to modify instances).

[cowtowncoder]

Started actual work, so this is now:

FasterXML/jackson-core#433