shares.happy is the wrong name of the measure

[zooko]

There is a configuration option named shares.happy which is how you control the servers-of-happiness value. It is mis-named! It should be named servers.happy. Of course, it belongs right next to shares.needed and shares.total, but hopefully placement and docs can make their intimate relationship clear. Also, shares.needed serves double-duty. It means both:

1. Number of shares necessary to reconstruct the file, and
2. Number of servers necessary to serve the file in a servers-of-happiness upload-quality metric.

Maybe that name should also be changed or at least documented even more carefully. Assigning to Brian. The next step on this ticket is for Brian to study the new servers-of-happiness feature (#778) and let us know what he thinks about it, both in general and in regard to this specific issue.