Feat: added full protobuf support + added tests

packages/mana/balance.go

packages/mana/balance_history_entry.go

packages/mana/balance_history_entry_test.go

packages/mana/balance_test.go

packages/mana/calculator_test.go

packages/mana/errors.go

packages/mana/input.go

packages/mana/input_test.go

packages/mana/proto/balance.pb.go

packages/mana/proto/balance.proto

packages/mana/proto/balance_history_entry.pb.go

packages/mana/proto/balance_history_entry.proto

packages/mana/transfer.go

packages/mana/transfer_test.go

packages/marshaling/marshal.go

packages/marshaling/types.go

packages/marshaling/unmarshal.go