Constraint code ported from WebAPI2. Tests are new.
Also a bunch of misc cleanup for constraints.
- Move IRouteConstraint to abstractions
- Fix namespace of a constraint
- Some general style cleanup
- use RouteValueDictionary in the public API
- Removed existing logger scopes as we want to minimize the number of scopes being created.
- Cleaned up tests related to removal of scopes.
- Added new log statements.
- Removed old logger structure base implementation and related tests. Added new tests also.