Working /push. Add /exec and /menu.
Working /push. Add /exec and /menu.

- Currently only cordova serve pushes are supported:
    /push?type=serve&name=<appname>&url=<serve URL>
- Run arbitrary Javascript in the app:
    /exec?code=<JS code, be careful of HTML encoding>
- Return to the main App Harness menu:
    /menu

apache/cordova-app-harness,apache/cordova-app-harness,feedhenry/cordova-app-harness,feedhenry/cordova-app-harness,guozanhua/chrome-app-developer-tool,feedhenry/cordova-app-harness,feedhenry/cordova-app-harness,guozanhua/chrome-app-developer-tool,apache/cordova-app-harness,apache/cordova-app-harness,guozanhua/chrome-app-developer-tool,guozanhua/chrome-app-developer-tool