title: AgGrid custom filter not created until interaction
body: <p>I have a custom filter component on a column in my grid. I've noticed that the filter component is not constructed until I click on the filter icon in the column header. This means that the data is not filtered according to my default settings (e.g., filter out records where <code>status == StatusEnum.Complete</code>). </p>
  
  <p>As a workaround, I've found that I can get a filter instance in the <code>onGridReady</code> event by calling <code>api.getFilterInstance('status')</code>, and this causes the filter component to be created and thereby apply default filtering.</p>
  
  <p>This workaround seems a bit clunky. The <code>filter</code> variable is unused in the <code>onGridReady</code> event, which causes warnings in the IDE / build. Another developer may come along and delete this line of code, thinking it is unnecessary.</p>
  
  <p>Is there a better way to force my custom filter to be instantiated when the grid is created? I'm using AgGrid 17.1 and Angular 4.4.</p>
  
  <p>The grid is configured like so:</p>
  
  <pre><code>gridOptions: GridOptions = {
      enableFilter: true,
      onGridReady: (event) =&gt; {
          let filter = event.api.getFilterInstance("status"); // forces the filter component to be constructed
          let data = this.loadAsyncData();
          event.api.setRowData(data);
      },
      columnDefs: [
      ...
      {
          headerName: "Status",
          field: "status",
          filterFramework: MyCustomStatusFilterComponent,
          filterParams: {
              valueGetter: (obj) =&gt; { return obj.data.statusEnum; },
              hideCompleteByDefault: true,
              ...
          }
      },
      ....
      ]
  }
  </code></pre>
  
  <p>I've set up an <a href="https://plnkr.co/edit/M9Zjz91Seys9JgWWJRX6?p=preview" rel="nofollow noreferrer">example that demonstrates the issue</a>. Note the "hack" on line 63 of <code>app.component.ts</code>.</p>