Fixed problems in haproxy-marathon-bridge script.

Fixed "unbound local variable" for services which have neither servicePort nor active tasks
Fixed problem with IP-address being used as port in HAproxy for services without a servicePort. Fix skips services where Marathon doesn't return a servicePort
Add app health display in application list of web UI

This commits add a health summary in the application list component of the weg UI.
To do this two new attributes are added to the /v2/apps JSON:

  tasksHealthy, tasksUnhealthy

These numbers are calculated in the MarathonHealthCheckManager by counting the
aggregated health check results of all tasks of an app.
Add app health pie component
Show over-capacity tasks in blue in health pie chart
Display health pie chart for suspended apps correctly in black