We use to have mu4e--contacts-hash, with name mapping to rank; that was
needlessly complicated since most completion engine sort alphabetically, making
the rank totally irrelevant (in practice, it doesn't matter much from the
end-user pov).
Anyway, simplify that part, maintain a set of contacts without any rank (which
what the server delivers now).
Also update the _default_ mu4e-contact-process-function to filter out anything
with 'reply' since it's not very useful for autocompletion.
Usurp more of the utils code than can be re-used without further dependencies in
helpers.
Split off specific parts in their own file.
After the helper/utils changes, update the rest of mu4e to take the changes into
account.
Dirk-Jan C. Binnema
Tassilo Horn