Nicholas Reuss

These changes try to align the error messages generated in the mjson jsonrpc handler with the error messages in the [JSON-RPC 2.0 Specification](https://www.jsonrpc.org/specification). An example of such behavior is seen...

Fixes #23

# Expected behaviour As per the [README.MD](https://github.com/PeculiarVentures/xml-core#xmlelement), the `XmlElementType` should have a nullable `localName` field that defaults to the name of the class. # Current Behaviour However, a typescript build...