Add ReactiveCollectionViewSource and ReactiveCollectionViewCell.
New internal class CommonReactiveSource.
Merge pull request #1 from meteficha/ReactiveCollectionView

New internal class CommonReactiveSource.
Safer disposing.
Formatting only.
Remove finalizer in CommonReactiveSource.

Also, seal class and remove virtual Dispose method.
Add InvokeCommand that is expression-based
Merge branch 'master' of https://github.com/reactiveui/ReactiveUI
Merge remote-tracking branch 'origin/pr/397'
Fixup the ReactiveUI_VSAll solution