add Signup_Platform__c = ios tracking to /mobile account create form succes

This PR addresses https://optimizely.atlassian.net/browse/MKT-784 of email names being `null` in confirmation emails after creating an account on /mobile.  Through investigating we found that we were not tracking the signup platform, therefore it is possible that emails were only being generated for users who were creating a mobile project in the product.  If so, the `null` field would have nothing to do with parameters passed from the /account/create - success on the /mobile page.

In order to pinpoint the problem, we also made a fallback for data values in the `oform globals tracklead` function, so name, phone number, and email values would default to empty strings if they are undefined.  A `window.debugger` option was also added to track data in production.

To debug, submit any form using `trackLead` and specify `window.debugger=true` prior to submission in the console.  For the /mobile for we would expect `Signup_Platform__c = ios` to be passed to marketo in the `reportingObject`
What does this do?