Introduced CompositeReflectionElementRefraction<T>,

which will (obviously) fulfill the role of a Composite, so that the other,
leaf IReflectionElementRefractions can be composed.
Made Composite...Refraction<T> an iterator,

for a Structural Inspection purposes.
Correctly implemented GetEnumerator methods.
Added a Guard Clause to the constructor.
Implemented Composite Refract method.
Added Null Guard to Refract method.
Documented CompositeReflectionElementRefraction<T>
Addressed a Code Analysis warning.