Add associatedOrganizations to event and event search apis.

Associated organizations includes the primary organization which is stored in the "organization" field along with all its ancestors. Duplication was required to simplify indexing of the "organization" field.

````json
{
      "organization":{
        "key":"aglrYXJtYWRlbW9yHwsSDE9yZ2FuaXphdGlvbiINY29sdW1iaWEucGFyaww"
      },
      "associatedOrganizations":[
        {
          "key":"aglrYXJtYWRlbW9yHwsSDE9yZ2FuaXphdGlvbiINY29sdW1iaWEucGFyaww",
          "name":"Columbia Park Clubhouse"
        },
        {
          "key":"aglrYXJtYWRlbW9yFwsSDE9yZ2FuaXphdGlvbiIFYmdjc2YM",
          "name":"Boys & Girls Clubs of San Francisco"
        }
      ]
}
````