Added a failing test for #475 (Parent lifetime scopes not properly propagating registrations to child scopes)
Removed further lookup of registrations for the registration's services within #475 (Parent lifetime scopes not properly propagating registrations to child scopes)

This causes bugs as it looks for registrations only within current ExternalRegistrySource(IComponentRegistry) while registrations can be overridden in nested lifetimescopes (ExternalRegistrySource(IComponentRegistry))
Refactored ExternalRegistrySource and removed unnecessary loop and variables within #475 (Parent lifetime scopes not properly propagating registrations to child scopes)
Amended new registration to cover only requested service, registrations for other services will be requested separately if needed. Was made within #475 (Parent lifetime scopes not properly propagating registrations to child scopes)
Enabled the unit test within #475 (Parent lifetime scopes not properly propagating registrations to child scopes)
Merge pull request #542 from alexandrnikitin/Issue475_BugInRegistrationPropagation

Fix for #475 (Parent lifetime scopes not properly propagating registrations to child scopes)