[FEATURE] improve memo support

- add MemoFormat property for memo
- MemoFormat and MemoType must be valid ASCII
- Memo content is converted on the serialization level
- add parsed_* version of Memo content if the parser understand the format
- support `text` and `json` MemoFormat

[FIX] double serialization overriding Memo contents

The copy made in from_json wasn't a deep copy
Historically we've accessed properties with dot notation unless it was impossible. In these cases it's possible. I kind of like the extra syntax highlighting in this case, so I don't feel strongly either way