webadmin: Add the option to create Posix/Gluster export domains

In the new storage domain dialog, added the option to add a Posix export
domain and a Gluster export domain

Change-Id: I4f39ed43026292011ae000f30806e02db9468d99
Signed-off-by: Tal Nisan <tnisan@redhat.com>
Bug-Url: https://bugzilla.redhat.com/1065963