webadmin: Redesigned Add/Edit Provider

Split the dialog into subtabs, one for general provider configuration
and one for plugin configuration specific to OpenStack Network
providers.

Moved around some UI fields, added gray background for primary fields,
toggled visibility of UI fields according to provider type and (for
the case of Neutron) plugin type, added small version ListBox, added
validation.

Change-Id: I1a9562407637f8b2252be876c05c6c78b5e25a02
Signed-off-by: Alona Kaplan <alkaplan@redhat.com>