feat(rxStatusSvc): Wrapper for rxNotify.

This provides a wrapper around `rxNotify` in order to make the repetitive usage of `{ type: 'success' }` type options less necessary.

It only works with singular messages today; the feature provided by `rxPromiseNotifications` is not being wrapped.

Thanks to @chriscantu for the initial version of the awesome service provided for vcenter-ui.
Thanks to @parlarjb for updating it with awesome features that makes the service even more usable.
They cannot be left as objects because the Status service is initialized once. And in `setStatus()` which is the bottom most function that gets called by all the others adds variables to `state` to let rxNotify know how to operate.

Since `state` there is equal to one of the `LOADING` or `ERROR` objects, if it gets modified once, it stays that way across the app. Making them functions returns a new instance every time so they are not modified previously.

This was Jay's finding after a few hours of friendship with the home key of his Canadian layout keyboard.