target: less implicit inclusion of "command.h"

target: less implicit inclusion of "command.h"

Lots of files still include it, often through needless
duplicate inclusion of "log.h"; sigh.

This cleans up the inclusion graph a bunch, so there are
fewer inclusion paths, but it doesn't change much otherwise.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>