First pass on the proxy interception abstraction
Create README.md
Added license headers to all files.
Renamed IProxied.cs to IMock.cs, changed target namespace to Moq.Sdk
Refactored fake mock base implementation to TestMock. Fixed failing proxy tests.
Added aspects to behaviors.
Add support for dynamically disabling aspects, and stopping pipeline behavior.
Add dynamic proxy to tests, for more realistic testing.
Extracted IAspect interface.
Refactored Behavior to avoid having an execute delegate.
Extracted IBehavior interface, and created DelegateBehavior to allow anonymous behaviors.