Implement codegen generating JDWP parsers/serializers

[michalgr]

Once #56 is completed, implement codegen tool using new JDWP description to generate data structures and serialization/deserialization logic, together with any python modules accompanying generated code, necessary to send and receive JDWP messages. At this point we should be able to open a socket and send raw JDWP messages to Java processes from Python REPL. We should also have a debugging tool snooping on JDWP communication between jdb (or any other Java debugger) and a Java VM.