webadmin: Pools main tab columns sorting

This patch adds sorting of fields in Pools main tab in webadmin.

Change-Id: I5ca199f769b23fe963d2b2bc087bfd9d63756818
Signed-off-by: Frantisek Kobzik <fkobzik@redhat.com>
Bug-Url: https://bugzilla.redhat.com/1104790