Factored the generation of JSON serialization from beeing part of the mirror objects into a seperate class. The purpose of this is to make it easier to change the serialization to contain object identification and references.

Added a test case for the script mirror and modified a number of the other mirror tests.
Review URL: http://codereview.chromium.org/16539

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1035 ce2b1a6d-e550-0410-aec6-3dcde31c8c00