XDCR should not auto-delete replications if the target bucket is deleted

If the target bucket for a replication is deleted, we quietly drop that replication and log the following:

Replication from bucket "beer-sample" to bucket "Empty" on cluster "Receiver" removed, since the target bucket "Empty" has been deleted

Although I can see scenarios where we wouldn't care about knowing this, I can also see a lot of scenarios where I would like to know about it. If someone has just nuked my DR bucket, I want to know about that ASAP on my prod cluster. Unless I'm parsing our logging (difficult) or manually reading the logs tab (unlikely), the only way I can see this from my prod cluster is to notice the absence of the replication in the XDCR tab (which might not be something I look at too often). Even then, if I have a few buckets replicating to a few clusters, the list in the XDCR tab is going to be pretty long - I'm not going to immediately notice one is missing.

Personally, I think the best answer would be to show the replication in red (or otherwise highlighted) in the list, and perhaps a warning popup too.