URBNG-519 - [WP] Implement queue of toast notifications
also:
* fixed TaskView header
* disabled back button while sending solution
* deleting old solutions - only the latest is stored in db
Merge remote-tracking branch 'remotes/main/windows_phone' into windows_phone

Conflicts:
	UrbanGameWP7/UrbanGame/ViewModels/TaskViewModel.cs
	UrbanGameWP7/UrbanGame/Views/TaskView.xaml
Merge pull request #150 from Maxikq/windows_phone

URBNG-519 - [WP] Implement queue of toast notifications