RPCGenerator depends on private API

[BenediktBurger]

The RPCGenerator in #3 depends on the private API of jsonrpc2-pyclient, as the baseclass is intended to include some message transfer methods, which are incompatible with pyleco.

[bilderbuchi]

The private API is from jsonrpc2pyclient._irpcclient import IRPCClient, which we inherit from.

Maybe useful: In what way are these message transfer methods incompatible?

When the dust has settled, it might be worth it to inquire about this upstream, maybe this points to a design change on their end, or there is a better way to achieve what we need?