* command/state list: list resources in nested and expaneded modules
A few distinct bugs fixed in here:
There was a bug in the logic checking if a given module was the child of
the targetAddr, now fixed. That resolved the basic issue where resources
in nested submodules were not listed.
The logic around allowMissing needed some tweaking to allow for empty
modules, as long as those modules had submodules with resources. state
list is the only command using allowMissing with false so this felt safe
to do.
Finally I extended the logic so list would included expanded modules,
which is to say giving module.foo would result in resources from
module.foo[1], module.foo[0], etc.
* update state list docs to show that module filtering includes any nested
modules
Several `terraform` subcommands include sub-sub-commands; with our old sidebar
system, viewing those took you to an isolated "island" nav sidebar, away from
the main docs. The new navigation will adopt all these pages, so we don't need
to exile the reader to odd places.