Menu creation could do with cleaning up and documenting

[timrowledge]

The creation of menus appears to have become a very complex process. It would be nice to try to simplify and document it.

[timrowledge]

@marceltaeumel try passing to Christoph?

[LinqLover]

Hi, I'm @LinqLover on GitHub. :-) What exactly do you consider complex? Some issues that would come to my mind include:

• Limited compatibility/polymorphy between MenuMorph, CustomMenu, and PluggableMenuSpec
• I always forget how to create submenus.
• The API for checkboxes (<off> etc.) is ... questionable. I'd myself be more in favor of a pluggable solution like this one: https://github.com/LinqLover/squeak-tracedebugger/blob/5d0ef83d940918e8ff5790e00dbc11b8eda1526d/packages/TraceDebugger.package/TraceDebugger.class/instance/mainContextMenu..st#L14-L18
• Afaik icons are currently hardcoded only and not customizable.

Apart from that, I found it pretty easy to browse through the construction protocol on MenuMorph and senders in order to explore the protocol ...