Introduce Application class

The newly added Application class represents a runnning application.
ApplicationProcessManager & RuntimeRegistry classes were removed.

Issue: Test system needs to be rewritten as it relies on the removed RuntimeRegistry.
Adapt in-browser testing system to the design changes.

Adapt in-Browser testing system to the RuntimeRegistry removal.
Added Application is_active() and Close() methods

Added Application is_active() and Close() methods
Prepare ApplicationService for managing multiple apps.

Prepare ApplicationService for managing multiple apps: it stores now scoped_vector of applications.
The ApplicationService interaface was cleaned.
Applcation Observer API was introduced to notify ApplicationService that the app has been closed.