Fixed item views recycling with multiple view types

HeaderFooterListAdapter#getItemViewType(int) wasn't returning the
correct view type for non-header/footer views.
Furthermore, in StaggeredGridView#obtainView(int, View) the new
generated StaggeredGridView.LayoutParams weren't set in the obtained
view (hence the recycled views all had viewType=0, and were never
re-used).