SOLR-13008 Indent JSON/XML formatted field value if indent=true and using DocumentTransformer

[epugh]

[epugh]

I've run "ant test" and while there are some failures, they don't appear to be related to this feature. I'm testing it now compiling and running Solr.

[epugh]

I added some nicer indenting. For a JSON block like:

{
"am I a teapot":true,
"lyrics":[
"I'm a little teapot","Short and stout","Here is my handle","Here is my spout"
]
}

with indent=false:

However, with 'indent=true`:

I'd love some feedback, as I am relying on Jackson to parse the XML or JSON string, and their is some assumptions on indentation levels that I made...

[epugh]

This whole PR may be too icky to really press forward with. Will think about it some more if htere is a better route.