Assemble data for a navigation tree
This function returns a nested dictionary structure reflecting the elements for a navigation tree. The tree will all sibling questions of the current context, the current module and all its module siblings, its parents up to the root module, and all modules at the root level.
Optionally a SQLAlchemy clause can be provided, which will be used to filter items shown in the tree. The current item and its parents will always be shown.
Each element is reflect as a dictionary item with the following keys: