Rename /extra API to /extras to keep it consistent with other APIs
Rename /config to /extras (without ident_hash)
Return the number of Collections and Modules for each subject in /extras
Merge pull request #127 from karenc/numbers-for-content-page

Numbers for content page
need version in human friendly filename
fix tests for version in filename
Merge pull request #128 from Connexions/export-filename-version

need version in human friendly filename
make subject a limit search - allow linit-only searchs
Merge branch 'limit-only-search' of github.com:Connexions/cnx-archive into limit-only-search