Add a progress indicator to examine for cloud based backups

What's the issue?
When using examine on a cloud based backup, the Rift index for the given vBucket must be downloaded (for each backup); the index may become quite large for large backups (possibly multi-gigabytes). We should have a progress indicator/reporter, or at least display a message to the user so that they know something is happening.

Possible Solutions
1) Find a way to avoid having to download the complete index, I don't think this is possible though e.g. we must know the location of the document in the data store.
2) Display a message, or a progress bar indicating that something is happening