Implement Location Alerts component

[philipmjohnson]

Please do work for this task in a branch called issue-110.

This is a real-time component that displays a description of most recent Alert observed for each location, along with the timestamp. It can be color coded to indicate age (i.e. red if the Alert was within the last hour, yellow if within the last day, green if older than a day.)

The user specifies the locations that they want the component to monitor for Alerts.