Changed ReactiveLinearLayout to ViewHolder so regular layouts can be used in the list adapter
Remove restriction on types that can be view models in ViewHolder - not sure why it was there. Also, enable a less-efficient view-callback for things that cannot be bound -- like ImageView.SetDrawable()
Merge branch 'rxui6-master' into listadapter-improvements

Conflicts:
	AndroidPlayground/WatchListActivity.cs
Move IViewHolder into Android directory
Add a LinkerOverrides file to control android sdk linking
Replace ViewHolder with something a bit better
Make ReactiveListAdapter way easier to use
Update WatchList to work correctly
Dat Stylo
We really can't do any better

Reading through ArrayAdapter, I don’t think we can actually tell the
list view anything other than, “something has changed”, as opposed to
iOS where we can tell it exactly what’s changed
Let people create non-ViewModel based layout view subclasses
Merge pull request #478 from reactiveui/listadapter-observer

Improved List Adapter Improvements
ViewHost => LayoutViewHost
Now we have stable IDs, tada
Merge pull request #472 from reactiveui/listadapter-improvements

Changed ReactiveLinearLayout to ViewHolder