WP-1281: Add PZP Dashbboard menu item to WidgetListActivity

Add PZP Dashbboard menu item to WidgetListActivity

Jira issue: WP-1281

This is an initial version that needs a couple of enhancements:
- check that the PZP has started, and wait (with the progress
  dialog) if necessary before attempting to launch the wrt view;
- use the port indicated in the PZP init notification instead of
  the default 8080.