title: Hide button on select datatable row in quasar-framework
body: <p>I am using quasar-framework <em>datatable</em> component what I want to hide title 
  and add button when select at least one row.</p>
  
  <p>I have this table below:</p>
  
  <p><img src="https://i.stack.imgur.com/k1PRp.png" alt="table without select row"></p>
  
  <p>when select row this happen:</p>
  
  <p><img src="https://i.stack.imgur.com/jusce.png" alt="table after select row"></p>
  
  <p>I want also to hide above add button, see code below</p>
  
  <pre><code>&lt;template&gt;
  
  &lt;!-- Table settings --&gt;
  &lt;q-table
      :title="tableTitle"
      :data="tableData"
      :columns="tableThs"
      :selection="selection"
      :selected.sync="selected"
      row-key="__index"&gt;
  
      &lt;!-- Add button slot --&gt;
      &lt;template slot="top-right" slot-scope="props"&gt;
          &lt;q-btn 
              @click="$router.push(addUrl)"
              icon="add_circle"
              size="14px"
              color="secondary"
              label="Add" /&gt;
      &lt;/template&gt;
  
      &lt;!-- Actions bar slot --&gt;
      &lt;template slot="top-selection" slot-scope="props"&gt;
         &lt;q-btn color="secondary" flat label="Action 1" class="q-mr-sm" /&gt;
          &lt;q-btn color="secondary" flat label="Action 2" /&gt;
          &lt;div class="col" /&gt;
          &lt;q-btn color="negative" flat round delete icon="delete" 
  @click="deleteRow" /&gt;
      &lt;/template&gt;
  
      &lt;/q-table&gt;
  
  &lt;/template&gt;
  
   &lt;script&gt;
      export default {
          props: ['tableThs', 'dataSource', 'tableTitle', 'addUrl'],
          data: () =&gt;({
            tableData: [],
            selection: 'multiple',
            selected: [],
          }),
          methods: {
             deleteRow () {
                this.$q.notify({
                    color: 'secondary',
                  icon: 'delete',
                  message: `Will delete the selected 
                  row${this.selectedSecond.length &gt; 1 ? 's' : ''} later, ok?`
              })
          }
      },
      mounted() {
          axios.get("/api/"+this.dataSource)
              .then(response =&gt; {
                  this.tableData = response.data.data;
               });
       }
   }
  &lt;/script&gt;
  
  &lt;style&gt;
     .row{
         margin-left: 0;
         margin-right: 0;
     }
     .q-table-bottom{
         border-top: 0;
     }
  &lt;/style&gt;
  </code></pre>
  
  <p>also I want a list with values of template slot like top-selection.</p>