Budgets by period follow-up

Follow-up of !776 (merged):

• Export/import budgets
• React to category creation/deletion on the client side directly instead of resetting every budgets in the store and relying on a new fetch to the server
• Move the sort by categories name to the client
• If a category is replaced by another which has no current budget, move the budget of the current category to the new one
• In the migration, clear the category budget after migrating it to dedicated budget model?