title: Mat-checkbox [checked]="false" does not work angular 6
body: <p>My mat-checkbox does not change value when using the <code>checked</code> input property.</p>
  
  <pre><code>&lt;mat-checkbox [checked]="false"
                formControlName="value1"&gt;Value1
  &lt;/mat-checkbox&gt;
  </code></pre>
  
  <ul>
  <li><p>Please explain the usage of the <code>checked</code> input property ie: what are the different methods for passing a boolean variable to the
  <code>checked</code> Input property?</p></li>
  <li><p>Are there ways to default selection using <code>FormControl</code>
  without needing to use the <code>checked</code> input property on the component?</p></li>
  </ul>