Work in progress portable library.

ReactiveCommand and ReactiveAsyncCommand moved to RxUI-Core
Renamed ReactiveUI_Portable to ReactiveUI.

Added _Net40 to .Net 4.0 projects.
Moved Validation.cs into RxUI-Xaml.
Updated projects to reference the Portable Library.
Lazy in its own file.
Linked Command classes and Interfaces into RxUI-Xaml for .Net 4.0
Fixed compile errors.

Fixed InternalsVisibleTo.
Temporarily handle unit test detection by returning false.
Change the namespace for PropertyChanging classes to work around namespace collision on .Net45. Need to think about the best way to handle this.
Renamed some collection methods.

Added IsEmpty normal property.
Make ScheduledSubject more flexible.
Added ListenIncludeLatest method to MessageBus to receive last sended message.
Merge remote-tracking branch 'origin/rxui5-master' into portable
Merge pull request #218 from reactiveui/rxui5-misc-jlaanstra

Misc improvements from jlaanstra/reactiveui
Fix broken project files.
Move RxUI-Routing into RxUI-Core and RxUI-Xaml.

Move Validation back to RxUI-Core.
Validation classes are not available on WP and therefore currently cause compile errors.
fix one reference to `CollectionCountChanged` -> `CountChanged`
Merge pull request #221 from wendazhou/rxui5-master-collection-name

fix one reference to `CollectionCountChanged` -> `CountChanged`
Validation framework rebuilt on top of INotifyDataErrorInfo.

TODO: Add hooks for ValidationAttribute on supported platforms.
TODO: Tests
Merge remote-tracking branch 'origin/rxui5-master' into portable
Define PORTABLE in Debug mode
RIP Silverlight and WP7
Move more things out of ReactiveUI.Xaml and into ReactiveUI proper
Rename Validation to ReactiveValidatedObject.

Enable ValidationObservable.
Make the ReactiveValidatedObjectTest run successfully with the rewritten Validation.
Fix coding style to comply with style guidelines in CONTRIBUTING.md