message: hide manage wallet nav link when no wallet is configured
diff: <ul class="uk-nav-sub">
  <li><a routerLink="/representatives" [queryParams]="" routerLinkActive="active"><div class="label">Representatives</div></a></li>
  <li><a routerLink="/configure-app" routerLinkActive="active"><div class="label">App Settings</div></a></li>
  - <li><a routerLink="/manage-wallet" routerLinkActive="active"><div class="label">Manage Wallet</div></a></li>
  + <li *ngIf="isConfigured()"><a routerLink="/manage-wallet" routerLinkActive="active"><div class="label">Manage Wallet</div></a></li>
  <li><a routerLink="/configure-wallet" routerLinkActive="active"><div class="label">Configure New Wallet</div></a></li>
  </ul>
  </li>
  