Adds IIntervaled to C5 interfaces
Adds IntervalComparer and IntervalBase
Renames IIntervaled's Overlap to FindOverlaps and introduces IntervalExtensions instead of IntervalComparer so IInterval gets extended instead of having to call the static methods on IntervalComparer
Adds NestedContainmentList, StaticIntervalTree and IntervalBinarySeatchTree to C5
Adds tests for intervaled.
Adds OverlapCount to interface, so tests will compile