Add IsEmpty to IReactiveList<T> and IReadOnlyReactiveList<T>.
Merge pull request #607 from reactiveui/isempty

Add IsEmpty to IReactiveList<T> and IReadOnlyReactiveList<T>.
Add ReactiveTableView
Merge pull request #608 from reactiveui/add_reactive_table_view

Add ReactiveTableView
Cast section info list to the matching IReactiveNotifyCollectionChanged<T>

Otherwise this always disables change notifications for section lists.
Merge pull request #609 from justin-factory/fix_commonreactivesource_cast

Cast section info list to the matching IReactiveNotifyCollectionChanged
Fix oops on Xamarin.Mac
Merge branch 'rxui6-master' of https://github.com/reactiveui/ReactiveUI into rxui6-master

# By Johan Laanstra (1) and others
# Via Paul Betts
* 'rxui6-master' of https://github.com/reactiveui/ReactiveUI:
  Fix oops on Xamarin.Mac
  Cast section info list to the matching IReactiveNotifyCollectionChanged<T>
  Add ReactiveTableView
  Add IsEmpty to IReactiveList<T> and IReadOnlyReactiveList<T>.