aaa: Adding namespace sorting

Adding sorting to namespaces presented at AdElementList model

Topic: AAA
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1120720
Change-Id: I24015f7116f0cd307f9969c89744fdab14f27fa6
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>