JsonWriter to offer control over when to newline

```
What steps will reproduce the problem?
1. I find there are too many newlines in pretty printing, I prefer the style
from http://jsbeautifier.org/
2. Provide setters for controlling if newline is output between array elements.

What is the expected output? What do you see instead?

No newline is output between array elements.

What version of the product are you using? On what operating system?

Gson 2.1 on Windows 7 64-bit with Oracle Java 1.6.0_31.

```

Original issue reported on code.google.com by `garydgre...@gmail.com` on 26 Jun 2012 at 12:12