First draft of prog-mode hook

php-mode is mostly working as desired, but apparently I broke
php-auto-yasnippet at some point in the past, so I'm not getting
auto-completions for it until I've done them manually.
Customize smart-dash-c-modes at startup

as doing it *after* turning smart-dash-mode on can result in a buffer
that should have the C-like hacks active not having them.
todo: replace "~/.emacs.d" with user-emacs-directory
Define .emacs.d-relative paths with user-emacs-dir

Also moves elisp-mode over to using my prog-mode hook, and fixes a few
elisp style errors flycheck showed me now that it's active in elisp buffers.

One of these days it'll be more widely used and I can just set it as my
prog-mode hook.
Fix error on startup

so yeah, that was smart.