Rename DefaultModelBinder to ModelBinder
Default model binder instance
Route table and route invocation should reference their declaring features.
Make ModelBinder an inherent property of Feature rather than IOC-managed.
Merge RequestContextBuilder and RequestProcessor
Make all stateless result processors singletons
Remove IRequestProcessor: YAGNI
Move IResultProcessor to root namespace. It's part of the core API.
Move FeatureSet and FeatureSwitchboard to Lifecycle namespace.

These are implementation details, not intended to form a part of the core API
and hence should not be regarded as stable.
Remove IRequestContext interface. It serves no purpose.