emacs, guix: add back most packages unavailable in Guix proper

namely, the following:

- boxquote
- company-ebdb
- delight
- ebdb
- erc-scrolltoplace
- message-x
- mwim
- shrink-path
- unkillable-scratch

they are now packaged in my guix-bandali channel, and hopefully soon
in upstream guix as well.