Health check response details are now visible in the dashboard.

UI changes:
- moved ping column above healthcheck
- added new column 'Details' with all details about the health check

Implementation details:
- Had to change the logic from simple success / error to always return
the JsonNode with the healthcheck information.
- The dashboard JS code is now looking for 'healthy = false' to decide
if a health check was successfull or not.
- introduced a new parent json node healthCheckResponse to have all
health check information under one parent instead of top-level mixed
with other response information.

I used a string-based lookup to check for any 'healthy = false' occurrences. This is arguable, feel free to replace this with an object based filter.

Preview:
![capture](https://cloud.githubusercontent.com/assets/7151335/4559212/a6b51174-4ee9-11e4-84f7-d64aeb88f8ee.PNG)