[Menu] Add user assistance to menu handling

[Guite]

It would be helpful if the new menu module would provide some helper functionality for supporting it's usage. Possible examples are tooltips explaining available actions and (particularly) means for describing attributes more easily. This issue collects ideas for that.

cc @rallek

[rallek]

I did not spent a lot of time in this new menu module. I did not get my first menu running right now. What I do need is the possibility to implement a menu node of content like menutree do have. Might be this already possible. If not I would vote to get this running again.

[MrMontesa]

I tested menu module a bit and like it. My main areas of interest are:

• cascaded menues
• permissions on menu items to suppress displaying
• ability easy pick the righr url

Is there some Javascript auto completion available? If you start typing an URL a pop-up with possible selections would be cool! Secondly I only used the URL attribute as I dont have clue what the other mean or do. Last but not least I'm bad on theme'ing. Some helper CCS classes to build horizontal, vertical, cascaded menues would be great.

[Guite]

For some potential causes of errors see #3750

[Guite]

The menu module should provide means for displaying/handling multi-level menus.

See https://github.com/zikula-modules/Content/issues/296#issuecomment-422672003 for examples.

[Guite]

Not needed anymore as dynamic menus are gone.