Re-implement "Vad har spenderats på min budgetpost?" on stats page

[foodelevator]

Instead of reading from the budget system like before, it should take all entries from the database as options to choose from.

[Blytungdev]

After a discussion with @DouglasFischer this should rather be implemented as a report (Resultatrapport). That is, you select either a primary or secondary result group and it should sum and list how much has been spent on all budget posts. Importantly, it should include both expenses and invoices

[Blytungdev]

This is important as it allows for greater flexibility in budgetting, and saves the Treasurer (me) a lot of time