* Garbage collection optimisations:
- Changed a few IEnumerable instances to IReadOnlyList. This avoids some unnecessary GC allocs that cast the Lists to IEnumerables.
- Moved cdf allocation outside of the loop to avoid unnecessary GC allocation.
- Changed GeneratorImpl to use plain float and int arrays instead of Array during generation. This avoids SetValue performing boxing on the arrays, which eliminates an awful lot of GC allocs.
* Convert InferenceBrain to use IReadOnlyList to avoid garbage creation.