[emacs,rc] Gnus + Isync + Dovecot configs, notmuch-emacs phase out

TODO: look into full-text search, using either notmuch or (c)lucene
https://ericabrahamsen.net/tech/2014/oct/gnus-dovecot-lucene.html
https://web.archive.org/web/20160713091633/http://roland.entierement.nu:80/blog/2010/09/08/gnus-dovecot-offlineimap-search-a-howto.html