Decision Hierarchy

Implementation of a so-called "Decision Hierarchy". This is a view to organise the different decision types: tactical, focus and given/strategic. Usually this is displayed in a triangle view. The categorization is already given when we enter the decisions and this is more of a focused view on the decisions.

Start by reviewing how decisions are categorized when they are entered and how existing decision data is exposed by the C# API. Define how tactical, focus, and given/strategic decisions should be organized in the proposed triangle view, then verify that the view groups existing decisions without changing their categories.

Written by the indexing model from the issue text.