[NavigationTiming2] Uploaded Navigation Timing 2 Spec

Per Action 101, http://www.w3.org/2010/webperf/track/actions/101, I have removed Section 4.4 from Performance Timeline and have added a new Navigation Timing 2 specification, http://dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming2/Overview.html.

Please review the Navigation Timing 2 specification carefully. As the processing model is slightly different from the previous version and as we would like the ability to add on to the definitions of existing attributes, I have redefined the attributes in this specification, as done in other specifications like the DOM specs.

Performance Timeline specification now has no open items or remaining feedback and can be moved to the CR stage.

Thanks,
Jatinder