zsh: Always show "dotfiles",

These should never have been hidden in the first place but thanks to a
real bug this has become a "feature"; abused by developers who believe
that dumping all sorts of data files, caches and configurations directly
inside the users $HOME is correct (as opposed to the more sensibly
structured /usr, /etc, developers don't dump everything under /etc...).
This de-facto standard needs to end.