title: Delete multiple items in array when position (index) is unknown
body: <p>I have the folowing Mongo db schema :</p>
  
  <pre><code>"Price_History" : [
      {
          "pr" : 62,
          "BookingDateTo" : "2014-08-05T18:41:35",
          "CollectionDate" : "2014-07-22T18:41:35",
          "Vendor" : "test",
          "BookingDateFrom" : "2014-08-04T18:41:35"
      },
      {
          "BookingDateFrom" : "2014-08-04T23:01:37",
          "BookingDateTo" : "2014-08-05T23:01:37",
          "pr" : 62,
          "Vendor" : "test",
          "CollectionDate" : "2014-07-19T23:01:37"
      }
  ],
  </code></pre>
  
  <p>this should be:</p>
  
  <pre><code>"Price_History" : [
      {
          "pr" : 62,
          "BookingDateTo" : "2014-08-05T18:41:35",
          "CollectionDate" : "2014-07-22T18:41:35",
          "Vendor" : "Trv",
          "BookingDateFrom" : "2014-08-04T18:41:35"
      },
  </code></pre>
  
  <p>The query should delete multiple items in an array if Price_History.CollectionDate is older then 2014-07-19T23:01:37 
  Finally the query should update all documents</p>
  
  <p>is that posible ?</p>