XD-1839: Named channels only allowed in full streams

Not sure about where exactly to report the error location. I chose the channel name itself (as opposed to the ">" symbol) 
I think it should be consistent between the source and sink case, but the current behavior seems to imply that in
```
http > queue:bar
       ^
```
if you change "queue:bar" to something else, it may succeed eventually, which is not the case.

Thoughts welcome