NetSerializer v4.1

- Allow adding already added types if the Type & TypeID match
- Add support for OnSerializing/OnSerialized/OnDeserializing/OnDeserialized
- Add constructors which take typemaps
- add GetTypes()
- Add GetSHA256()
- Fix serialization of System.Object

NetSerializer v4.0

- Optimize Decimal serialization
- Optimize Nullable serialization
- Rewrite of the test apps
- Rewrite of the main serializer
  * create serializers on demand, instead of all at initialization time
  * (de)serialize values directly, without boxing
- NoOpSerializer
- Experimental support to add more types after init

NetSerializer v3.1

Some optimizations which give a small but clear performance improvement (on my
tests).

NetSerializer 3.0

Support instancing the Serializer

Minor error checking and cosmetic improvements

NetSerializer v2.0

Support for custom serializers

Fix codegen when number of types > 256

String serialization optimized

v1.3

* Support IDeserializationCallback
* .Net 3.5 compatibility fixes

v1.2

* Use MPL-2 License
* Option to compile without unsafe code
* Minor cleanups