webadmin: Refactored import VM/Temaplate dialog

Refactored the import VM/Template dialog to let the clone and collapse
snapshots options be set individually for each entity rather than for the
whole of the entities to be imported

Change-Id: I8fb5139f43370705081675ab5ffa1552c16c3082
Signed-off-by: Tal Nisan <tnisan@redhat.com>