webadmin: [RFE] Display Address Override

Detailed description:
http://wiki.ovirt.org/wiki/Features/Display_Address_Override

The following gui changes has been introduced:
- Enriched the HostPopupView by a Console side tab in which
  the display address override is defined (a checkbox which
  enables it and a text field with hostname or ip validation
  to actually define it)
- General subtab of the Cluster main tab enriched by a warning
  message which is shown when some hosts in the cluster
  overrides the display address and some not
- Hosts subtab of the Cluster main tab enriched by a column
  which shows if the specific host has or has not overridden
  the console address

This patch also extracts the InLineAlertWidget (the warning
from the General subtab of the Hosts main tab) to a standalone
reusable class.

Change-Id: I47674a1ecde457c51934e8ad262639567902a9be
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>