Group currencies in the Summary screen

The Summary screen currently presents an overwhelming amount of flatly arranged information. We should categorize entries under respective currencies, allowing users to expand any of them.

Start by locating the Summary screen implementation and the model or UI entry point that supplies its entries. Review how currencies are represented and how the current flat list is rendered. Done means entries are categorized under their respective currencies and each category can be expanded or collapsed.

Written by the indexing model from the issue text.