Use more efficient serialization format for integers

Use variable-length sign+magnitude format for integer serialization (identical for short, uint etc.)
Re-focus reflection around native integer types (short, int, long) instead of fixed-size types
Make the default Serializer easily replacable
Add SerializationManager to be more Enterprise(R)(TM). All rights reserved.

On a more serious note, this makes it possible to nicely hook serialization for different types.