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.
The page should not show any headings which don't have any
winning investments. The "no content" message should only be
shown when there are no headings with investments to avoid an
otherwise blank page.
__Note:__ in the main @headings query, _both_ #includes and #joins
are needed to:
1. eager load all necessary data (#includes)
and
2. to perform an INNER JOIN on milestones to filter out investments
with no milestones (#joins).
This commit makes 3 changes:
1. Extracts a query into a helper for clarity and DRYness
2. Adds a `.where` clause to filter investments based on their
(current) milestone status
3. Fixes a bug where investments would be rendered as many times as
milestones associated to an investment
