fix(bootstrap): add search role

This is a fix for a severe error found using the Google Accessibility Developer Tool audit:
Elements with ARIA roles must ensure required owned elements are present

src/bootstrap/select.tpl.html

@@ -1,6 +1,6 @@
 <div class="ui-select-container ui-select-bootstrap dropdown" ng-class="{open: $select.open}">
   <div class="ui-select-match"></div>
-  <input type="search" autocomplete="off" tabindex="-1"
+  <input type="search" role="search" autocomplete="off" tabindex="-1"
          aria-expanded="true"
          aria-label="{{ $select.baseTitle }}"
          aria-owns="ui-select-choices-{{ $select.generatedId }}"