[2.2,API, performance] Compact API request to get a limited set of information, such as hostname and system_id

This is a feature request.

At this moment, to get all pairs of hostname and system_id, `maas admin machines read` is used with maas-cli. However, the request takes a long time, for example, 22 seconds with 30 nodes, 1.5MB and 40,361 lines. With over 100 nodes, it takes more than a minute actually. Because it dumps detailed information including disk and network interfaces.

It would be nice if MAAS had an API request to get a limited set of information (compact mode?).

$ time maas admin machines read -d | wc -l
200 OK

  -Content-Encoding: gzip
     Content-Length: 1509654
   Content-Location: http://localhost/MAAS/api/2.0/machines/
       Content-Type: application/json; charset=utf-8
               Date: Thu, 13 Apr 2017 02:18:02 GMT
             Server: TwistedWeb/16.0.0
             Status: 200
               Vary: Authorization,Accept-Encoding,Cookie
    X-Frame-Options: SAMEORIGIN
    X-Maas-Api-Hash: <snip>

40361

real 0m22.781s
user 0m2.372s
sys 0m0.112s