Refactor to use ergo

[oubiwann]

This'll be a biggie, but it will allow for much easier 2-way comms between the LFE undertone/undermidi servers and the Golang midiserver.

Features/tasks:

• [x] #33
• [ ] Revisit use of ergo in rpc client code with an eye towards proper refactoring
• [ ] More to come ...

See:

• https://github.com/ergo-services/ergo
• https://github.com/ergo-services/ergo/tree/master/etf
• https://github.com/ergo-services/ergo/tree/master/node
• https://github.com/ergo-services/ergo/blob/master/examples/application/demoApplication.go
• https://github.com/ergo-services/ergo/blob/master/examples/supervisor/demoSupervisor.go
• https://github.com/ergo-services/ergo/blob/master/examples/genserver/server.go

[oubiwann]

Current use of erlang_go:

pkg/erl/datatypes/datatypes.go: erlang "github.com/okeuday/erlang_go/v2/erlang"
pkg/erl/messages/command.go:    erlang "github.com/okeuday/erlang_go/v2/erlang"
pkg/erl/messages/handlers.go:   erlang "github.com/okeuday/erlang_go/v2/erlang"
pkg/erl/messages/midi.go:       erlang "github.com/okeuday/erlang_go/v2/erlang"
pkg/erl/messages/response.go:   erlang "github.com/okeuday/erlang_go/v2/erlang"
pkg/erl/packets/packets.go:     erlang "github.com/okeuday/erlang_go/v2/erlang"