docs about Rest vertical position

[Kieren MacMillan]

Hi all,

I was answering a user's question on the FB group, and noted that in the docs, 
we suggest

    “To explicitly specify a rest’s vertical position, write a note followed by 
\rest.”

While this is a useful thing to know about, I don't personally believe it's a 
best practice: it mixes content with presentation, it doesn't play well with 
\transpose, etc.

I'm not necessarily suggesting that we avoid pointing out this feature. I'm 
just wondering if anyone else agrees that we should point out the downsides, 
and give alternative ways of accomplishing the same task? If so, I can put 
together some draft verbiage for a discussion starting point.

Cheers,
Kieren.