webadmin: Fixed sorting in Cluster and Datacenter Networks subtabs

Sorting now treats numeric subsequences in network names as such. Also
fixed minor (unreported) bug having to do with sorting in the
assign/unassign networks popup window.

Change-Id: I8432b61ae79195a454eec50e5322182103f02527
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=920209
Signed-off-by: Lior Vernia <lvernia@redhat.com>