Fix for #278.

Adds protected virtual void methods to raise events and comply with .NET best practices around events through all of ReactiveUI.
Rename some namespace references, so we build succesfully.
Merge remote-tracking branch 'origin/rxui5-master' into events-virtual-methods
Style Fixups
Clean up the View Locator code a bit
Fall back to the view that doesn't specify an orientation

If the developer doesn't want to use orientation-specifc views, try to
resolve the non-orientation specific view
Merge pull request #335 from reactiveui/view-locator-fallback

Fall back to non orientation-specific views
Reintroduce read-only interfaces

Have CreateDerivedCollection return interface for maximum
flexibility going forward in RxUI5.

Makes IObservedChange and IReactiveNotifyPropertyChanged
covariant.
Add xml docs for new interfaces
Including move notifications in interfaces
Make RDC implementation internal
Merge pull request #336 from reactiveui/derived-readonly-interfaces

Read-only interfaces for derived collections
Version bump to 5.0.1 Final
Merge branch 'rxui5-master' of https://github.com/reactiveui/ReactiveUI into rxui5-master