Custom Message Serialization and Compression

Here's a simple, working implementation of Customising Serialization and applying compression to the BrokeredMessage. Provides for:
- DefaultSerializer: DataContractSerializer (as ServiceBus provides OOTB)
- JsonSerializer using JSON.NET
- NullCompressor
- DeflateCompressor
- GzipCompressor

Shout out to @gertjvr for the original implementation of the Custom Serialization.