feat(rxStatus): attr edit for success/error banners; Resolves #420

Addresses issue #420, adding timeout and repeat=false attributes to success banners and a repeat=false attribute to error attributes. Once this is merged in, I will need to delete `status.js` and `status.spec.js` from encore-cloud-ui and remove the import of `status.js` from encore-cloud-ui's `index.html`.
So to follow-up, there was a long conversation on the slack channel going back and forth on this. Basic takeaway is that the biggest concern for vCenter was regression testing errors; we edited our pageStatus method to address timeouts here. https://github.com/rackerlabs/encore-cloud-ui/pull/111

This PR was submitted to encore-ui mostly to handle a lack of design pattern continuity so even if we backed off on this PR, this issue would pop up again in the future. TL;DR, the right thing to do is to change vCenter success messages a 5 and edit test cases appropriately.