Message factory (#286)

* Added plugin structure and DB sequence number. WIP

* First version of transaction factory and builders for payloads #275

* Move marshalutil to hive.go

* Refactor existing code (before binary) to use new hive.go/identity #282

* Adjust binary code to use hive.go/identity and remove signature/ed25519 #282

* Adjust moved files from merge to use hive.go/marshalutil

* Adjust moved files from merge to use hive.go/identity and hive.go/crypto

* Adjust to merged changes

* Rename to MessageFactory

* Use local identity and tip selector

* Rename package

* Add tests

* Changed BuildMessage to receive an interface value instead of pointer

* Refactoring and comments

* Fix: fixed issues due to refactor

* Refactor: refactored the code

* Refactor: removed unnecessary messagefactory plugin

* Refactor: cleaned up code

* Feat: made spammer use messagefactory

* Refactor: refactored method name and docs

* Refactor: additional refactor

* Refactor: go mod tidy

Co-authored-by: Hans Moog <hm@mkjc.net>