Implementing an extensible set of classes for the KeyCommands.

Todo :
- Implement a "register" behavior (when everything is done, each command handler will be able to register the commands it can handle)
- A few IKeyParamterManager implementations for the different command handlers
- INotifyPropertyChanged implementation
- A set of templates and the corresponding data template selector.
Creating a SendKeyCommandParameter, starting to implement  INotifyPropertyChanged
KeyCommands : implementing INotifyPropertyChanged, linking the model to the View.

It works, but it's still pretty ugly
Key configuration refactoring : step 1.
Adds Logs with ActivityLogger and add a FastObservableCollection that raises collection changed only when full items are added
Replace items (bugs some times)... StringSending event to black carte index blinking
Modify "GetNextElement" to split VMZoneSimple to VMSplitZone
GetUpParent > use the correct parent
Merge branch 'develop' into f-splitscrolling-onfly

Conflicts:
	Plugins/Accessibility/KeyScroller/KeyScroller.cs
Computes the TextualContext string to feed to predictor in an extensions method availble on the CK.WordPredictor.Model library.
The prediction text area does no longer updates the prediction text bus.
Merge branch 'f-predictor-area-blink' into f-predictor-fix
Throttle property changed event (250 ms). Should be customizable ?
Merge branch 'f-predictor-keyboard-listening' into f-predictor-fix
remove useless using
Merge remote-tracking branch 'origin/develop' into f-predictor-fix

Conflicts:
	Plugins/Prediction/CK.WordPredictor.Sybille/SybilleWordPredictorEngine.cs
	Plugins/Prediction/CK.WordPredictor/TextualContext/TextualContextService.cs
Retry failed predictions
Changes IPredictionTextAreaService interface : remove IPropertyChanged, and update it to a strongly typed bus to publish PredictionAreaContent event args
Removes INotifyPropertyChanged from ITextualContextService. ITextualContextService implements its own Events
Replaces IReadOnlyList by ICKReadOnlyList