title: Change the icon used by v-toolbar-side-icon?
body: <p>Is it possible to change the icon used in by <code>v-toolbar-side-icon</code> to a custom one?</p>
  <pre class="lang-html prettyprint-override"><code>    &lt;template&gt;
        &lt;v-toolbar&gt;
          &lt;v-toolbar-side-icon&gt;&lt;/v-toolbar-side-icon&gt;
          &lt;v-toolbar-title&gt;Title&lt;/v-toolbar-title&gt;
          &lt;v-spacer&gt;&lt;/v-spacer&gt;
          &lt;v-toolbar-items class=&quot;hidden-sm-and-down&quot;&gt;
            &lt;v-btn flat&gt;Link One&lt;/v-btn&gt;
            &lt;v-btn flat&gt;Link Two&lt;/v-btn&gt;
            &lt;v-btn flat&gt;Link Three&lt;/v-btn&gt;
          &lt;/v-toolbar-items&gt;
        &lt;/v-toolbar&gt;
      &lt;/template&gt;
  </code></pre>
  <p>There is no props or documentation for that component itself in <a href="https://next.vuetifyjs.com/en/components/toolbars" rel="nofollow noreferrer">https://next.vuetifyjs.com/en/components/toolbars</a></p>