Implement Failed Messages indicator per Endpoint

[dannycohen]

As Opie, when the failed messages indicator is red, I want to drill down and see in which endpoints messages failed to be delivered, so I can take corrective actions.

Visualization:

1. Clicking on the Failed Messages indicator displays an indicator for each logical endpoint
2. For each endpoint:
   • endpoint should be green if it has no active failed messages alerts
   • endpoint should be red if it has ome or more active failed messages alerts
   • endpoint name should appear below the endpoint failed messages indicator icon
   • number of active failed messages alerts should appear next to the endpoint name

Notes:

• Follow up to #46, with the added detail of drilling down to the endpoint level indicator

Demo / Acceptance tests:

Case 1:

1. Run the Video Store sample (5 endpoints)
2. Cause 5 messages to fail in the "Sales" endpoint, and 3 messages to fail in the "eCommerce" endpoint
3. The Failed message indicator is red, and the number "8 msgs in 2 endpoints" appears below it
4. Click on the Failed message indicator
5. The endpoint failed message indicators appear; 2 endpoints are red (Sales and eCommerce) and the other 3 are green
6. Next to the Sales and eCommerce endpoints appears the number of active failed message alerts relevant to them (5 and 3, respectively)

[dannycohen]

Moved to: https://github.com/Particular/ServicePulse/issues/11 (implement a similar experience for Failed messages as well as heartbeats)