title: @swimlane/ngx-datatable virtual scroll works only with cached rows
body: <p>@swimlane/ngx-datatable virtual scroll works only with cached rows. Cached rows keep in the array. In my case, the number of that rows can be more than 10 million. How to not cache that rows and use the virtual scroll?</p>
  
  <p>Reproduction of the problem:</p>
  
  <p>1) Example of current behavior virtual scroll without cached rows: <a href="http://prntscr.com/kw9q51" rel="nofollow noreferrer">http://prntscr.com/kw9q51</a> </p>
  
  <p>2) Repo: <a href="https://github.com/DmitriyIvanko/ngx-datatable-example/blob/master/src/app/app.component.ts" rel="nofollow noreferrer">https://github.com/DmitriyIvanko/ngx-datatable-example/blob/master/src/app/app.component.ts</a></p>