/changes/: Permit multiple queries at once

Allow the client to specify more than one q parameter. When there
is more than one query defined the result is an array of arrays,
one per query in the same order the queries were given in.

This query now approximates how to show a user's dashboard:

$ curl -n --digest 'http://127.0.0.1:8080/a/changes/?q=is:open+owner:self&q=is:open+reviewer:self+-owner:self&q=is:closed+owner:self+limit:5&format=JSON'
)]}'
[
  [
    {
      "project": "tools/repo",
      "branch": "master",
      "id": "I37f758e238c2dbc891a0d876547cb7acc29fc7f7",
    }
  ],
  [],
  []
]

Change-Id: I1914a9971c519a5539ce0fbe56c6d5776d7bd72f
1 file changed