WebUI should (somehow) indicate a problematic directory entry

#### Version information:
`Any`

#### Type:
`Enhancement` ( arguably `Bug` )

#### Severity:
`Medium`

#### Description:

When faced with a duplicate name in a directory, the UI does not signal in any way that something is amiss. There should be some sort of indication ( a red exclamation mark or something ) to visually alert the user "hey, watch out". I am not able to build FUSE locally, so I do not know how things behave there: likely needs to be investigated as well.

Here is an example DAG: https://ipfs.io/ipfs/zdjA8bKXBUttGJ7aXtG3DeuHYtAVXNj1jA5sKuscTJ1nk1xL9

This issue is tangentially related to https://github.com/ipfs/go-ipfs/issues/1710. There is also a somewhat explicit policy in the [IPLD spec](https://github.com/ipld/specs/tree/master/ipld#duplicate-property-keys), but if the UI doesn't show anything about it - this is still a problem.

P.S. In case this is deemed a security issue that should not be public - feel free to delete this bugreport. I tried to use the `security@` contact [two](https://botbot.me/freenode/ipfs/2017-09-01/?msg=90558796&page=2) [times](https://botbot.me/freenode/ipfs/2017-10-06/?msg=91999525), but never received a response, so decided to file here before I move on.