Fixes for Google Drive Picker integration

- Directive no longer needs to use scope.$apply in Google Drive Picker "picked" event handler as there was a $digest error now that services are being used in Google Drive Picker
- Fixed reset() function to properly apply some default settings to the scope.spreadsheet by using angular.extend for a shallow copy
- Updated e2e test HTML to ensure google client api or gapi-mock get loaded last
- gapi-mock.js updated to include handleClientJSLoad and remove unnecessary window.pickFiles and window.dialogCancel functions as these pertain to e2e tests in Google Drive Picker only