The new CSV report was more configurable and could work on proposals,
processes and comments. However, it had several issues.
In the public area, by default it generated a blank file.
In the admin section, the report was hard to configure and it generated
a file with less quality than the old system.
So until we improve this system, we're bringing back the old investment
CSV exporter.
This commit reverts most of commit 9d1ca3bf.
Note that we are relying on the existing `sort_by_name`[1] method in the `Budget::Heading` class.
This method sorts by DESC group name first and then ASC heading name.
[1] https://github.com/AyuntamientoMadrid/consul/pull/1875
ApplicationHelper#format_price and Budget#formatted_amount has the same
objective and code, but the Budget#formatted_amount method also uses the
currency of the Budget to correctly give currencies format.
By replacing usage of format_price with formatted_amount we can remove
format_price and have a single location for currency format logic.
