Updated front-end to blink branch 1507.
Patched front-end/inspector.html

Added node-inspector specific scripts.
Reuse stubs and commands from webkit-inspector.

Use original InspectorBackendStub and InspectorFrontendHostStub.
Generate InspectorBackendCommands.js from protocol.json.
Use original inspector.html instead of index.html.
Rework backend to support the new frontend.
Upgrade node-inspector backend after front-end update.