Rename TJSONProtocol.java -> TSimpleJSONProtocol.java

Rename TJSONProtocol.java -> TSimpleJSONProtocol.java

Summary:
Chad Walters is developing a full-featured JSON-based protocol for Java,
so we're renaming the existing protocol to something more descriptive.
I also edited the file to rename the class and add to the header comment.
I have no idea if Subversion does explicit rename tracking, or if
git svn is smart enough to mark renames as such, but I would predict
"yes" to both.  Let's find out.

Reviewed By: mcslee, jssarma

Test Plan: Ran "ant" in lib/java

Revert Plan: ok

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665492 13f79535-47bb-0310-9956-ffa450edef68