Reflect Wiki's deep nesting in the structure sidebar

Description

Wiki pages allow deep nesting, but Wiki structure displayed in the sidebar does not represent it. It displays as if it was only one level nesting.

Page under title foo/bar is displayed as foo -> bar, but foo/bar/baz is displayed as foo/bar -> baz.

Proposal

Display multi-nested Wiki structure in the sidebar.

Links / references

Documentation blurb

(Write the start of the documentation of this feature here, include:

1. Complex projects require complex knowledge database structure.
2. Solution is to provide nesting deeper than one level.