Various Slurper/Builder Improvements

* Adds writeTo(File file) and writeTo(File file, boolean pretty) to JsonBuilder. (Needs Documentation, but I'm using GNU Nano to write this stuff, so I will do that later.)
* Documentation Fix for ConfigSlurper

More is to come. I will update this PR as soon as I add stuff.

Also, should I squash all these commits once I am done?