Fix functionality of the Memberships widget
    
    This commit fixes a number of small issues with
    the membership widget.
    
    First (Fixes #418) was kind of the source of a lot
    of the other issues. This widget behaved differently
    when on a user hub vs a group hub. On the group hub
    it showed who was a member of that hub. On a User hub
    it showed what hubs the hub was a member of. In this
    commit, the widget just focuses on showing who is a
    member of the hub. Of course, on a user hub there will
    be only one member, the user.
    
    Fix #417 -- Previously, the label that changed from
    member to owner if a member was an owner did not work.
    All users were listed as members only. This commit fixes this
    
    Fix #416 -- Previously the links to users listed in the widget
    were not showing or working. This was because the widget was
    using member.name rather than member.username. This is now fixed.
    
    Fix #415 -- Previously the title of the widget was "hubs". This
    has now been changed to "Members"
    
    Fix #414 -- Previously when trying to add the Membership widget
    to a hub, it was listed in the list of widgets as "Hubs" it is now
    listed as "Memberships"
    
    Fix #357 -- Previously the links in the Memberships widget used
    hard links rather than url_for. this is now fixed.
    
    Additionally, the avatars on the view more modal in this widget
    were extremly stretched vertically. This commit fixes that issue
    too.
    
    Signed-off-by: Ryan Lerch <rlerch@redhat.com>