Mentioned CreateNamedScope and removed some misleading text from Readme

Mentioned CreateNamedScope
Removed inaccurate characterizations 
Removed speculative text to keep text brief

Also propose new description in line with content: This extension enables Bindings to define Scopes. Dependencies can then define that they want to use such Instances as their Scope. Also offers a programmatic equivalent which can be used to deterministically manage a composition tree for request processing scenarios.