Tidy ext.eventLogging.{subscriber.js,core.js,jsonSchema.css}

* Rename 'dfd' to 'deferred', for readability.
* Better comments for ext.eventLogging.subscriber.js.
* Factor out titleCase and handleTrackedEvent.
* Remove a line of dead, commented-out CSS code.

Change-Id: If6027a4cc8f6a83bf72b4f93af44101a3df9aff0
Merge "Tidy ext.eventLogging.{subscriber.js,core.js,jsonSchema.css}"