Add Notifications to Web Interface

[linknum23]

We should add a small set of icons to provide useful notications via the user interface (adding similar information to the api as well)

• [x] New release available (added to info->latest_release) related to #324
• [x] Show connection status (#267)
• [ ] Announcement in progress (info->announcement)

Additional info the we should find a place for:

• [ ] Show latest release with button to navigate to updater
• [ ] Show disconnected info (disconnected from amplipi or internet access unavailable?)
  • Whether or not Internet access is available to amplipi is something that is reported in status->info->online

[linknum23]

The backend support for this is being added in #356