`all` is a confusing and unclear option name; `instrument` was better

I got really confused when `all` is necessary; at first I thought it instruments even files that aren't selected for coverage, and without it things in `include` (but not `exclude`) get instrumented?

But it seems like the old `instrument` option was just renamed to `all`.  The old name was clearer, it really doesn't make sense that it was renamed this way.