Shell/3909

A massive purge of content.

This removes all articles except those that were on a whitelist put together by @squamosity and @nsanchez. We are loosing a lot of articles with good content which we will certainly bring back. But the point of this was to get to a working state, where we can be sure we aren't leading users with descriptions of features that do not exist on our system.

After the first commit, the remaining are just to fix up the help pages that were left over and get them into a consistent state.

[endlessm/eos-shell#3909]