Refactored project page view model to remove clipping when landing

[vincentcastagna]

• Added task notifier for the project (to be able to display errors)
• Changed which task should be notified to the user on the view
• Changed flow of OnNavigatedTo
• Removed some useless loading flag, and added new one to fix error display

Aside :

• Moved the property changed of the internet faulted to be triggered before classical error (avoid both to be displayed)