Support multiple tx versions

[jasny]

For most transaction types, there are multiple versions. The version determines the binary structure. Some fields may not be available in older versions. Also, v3 is required to support sponsored transactions.

Please add version support for all transaction types. The default version should be 3. It should be possible to modify the version property. When calling toBinary() check the tx version and switch to the correct implementation. Either use multiple methods within the tx class (like python does) or use Pack classes for each tx type and version combination. If an unsupported version is used, throw an exception.

The version should be correctly set when creating the tx object from json.