Allow extra_menu: tag for nested menus.

[portnov]

This allows to process extra_menu: tags for nested menus in index.yaml.

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Put an x letter in each brackets when you're done this item:

• Code changes complete.
• Code documentation complete.
• Documentation for users complete (or not required, if user never sees these changes).
• Manual testing done.
• Unit-tests implemented.
• Ready for merge.

[Durman]

I guess this method can be used instead

sverchok/ui/nodeview_space_menu.py

Line 272 in b7b06eb

def walk_categories(self) -> 'Category':

Suggested change

	for cat in add_node_menu:
	if getattr(cat, 'extra_menu', '') == self.menu_name:
	cat.draw(_self.layout)
	elif isinstance(cat, Category):
	for item in cat:
	if getattr(item, 'extra_menu', '') == self.menu_name:
	item.draw(_self.layout)
	for cat in add_node_menu.walk_categories():
	if getattr(cat, 'extra_menu', '') == self.menu_name:
	cat.draw(_self.layout)

Probably I preferred the first variant for performance.

[portnov]

ok, updated.
I had to add a parameter to walk_categories to include CustomMenu items in order to include Groups and Presets into 5 menu.

[Durman]

I did not realize that Custom Menus are also needed. Then using walk_categories it not best choice. The idea was that the method returns only categories. The annontation also show this. And there is recursive call which makes things a bit more complicated. I can suggest than:

sub_categories = [add_node_menu]
for _ in range(1000):
    cat = sub_categories.pop()
    for cat_item in cat:
        if getattr(cat, 'extra_menu', '') == self.menu_name:
            cat_item.draw(_self.layout)
        if hasattr(cat, '__iter__'):
            sub_categories.append(cat_item)
    if not sub_categories:
        break
else:
    log('There is some problem')