wish: budget report categories by month

[Romain]

Hi,

# Pain point
In the budget report, it is only possible to display :
- Total by categories on the period (Mode = Total)
- Total by month on the period (Mode = Time)

User (I) don't have a detailed view of the budget.

This view is great to make an assessment of the budgeted year : which month have been bad or good. This knowledge is important to make the budget of the next year.

# Solution
Must have :
New mode ("Split" for example). This mode will display data :
- Row : categories
- Column : months ; each month will be split in sub-columns (spend, budgeted, result €)

Could have :
Parameters to show result (€) or realised (%)