opam_admin.top: forgot to commit mli
Use 'authors' by default rather than 'author'

What was the original reason for the dual name for this field ? Seems like
a compat hack for 1.0/1.1
Opam show: add the dev-repo and bug-reports fields
After pin-edit, display a message to tell the user how to re-edit
Merge pull request #1476 from OCamlPro/small-ui-fixes

some better messages, more info available on `opam show`, normalise to `authors`...