webadmin: import iSCSI data storage domain dialog

Import domain dialog ->
added a view for import iSCSI data domain which consists of two panels:
* Target discovery.
* Storage domains that are candidate for import.
Feature page:
http://www.ovirt.org/Features/ImportStorageDomain#GUI_Perspective_2
Change-Id: If379f5e41544fda90cb3e31e38784b768c994e5c
Signed-off-by: Daniel Erez <derez@redhat.com>