Add ERR_CONFIG error code for problems reading config files
lib/cli++: Add helper function for outputting fatal system errors
Make system errors on reading config files fatal (with useful message)
send: Improve error messages when reading config files
send: Reorganize exec_remote to be a member of struct remote
nullmailer-send: Reword multiple remote documentation to match actual behavior
queue: Rename parameter to validate_addr to avoid confusion
queue: Drop the remapadmin boolean

It is completely unneeded, since adminaddr will always be non-empty when
it would be true.
Bump version to 1.14
Add news note for error handling changes
Drop extraneous -q in tests/queue/rewrite
queue: Add an "allmailfrom" control file, to force a fixed sender