implement startup loading events (bug 1024014)

The docs are at https://developer.mozilla.org/en-US/Apps/Build/Performance/Firefox_OS_app_responsiveness_guidelines

There some ambiguity in what the events mean especially since we show the splash screen up until everything is loaded. I decided to just trigger/group some of the events together once the splash screen is loaded.
you'd have to read https://developer.mozilla.org/en-US/Apps/Build/Performance/Firefox_OS_app_responsiveness_guidelines

there was some ambiguity in when i'm supposed to trigger the events. am I supposed to trigger them if there's a splash screen over them? i'm not sure, so i have two different pieces of code where for one i ignore the splash screen for some events, and for the other i consider the splash screen.