Allowing & to appear in CDATA section

Right now, if an XML String has an `&` in a CDATA section running Indent XML doesn't do anything.

After removing `CDATASTART`, I'm looking in the CDATA section for any `&` and converting it to `&amp;` before removing `CDATAEND`.

Then, when `CDATASTART` is added back in, I revert the `&amp;` to `&` before adding `CDATAEND` back in.