Implement new order and add new cards to adv data cards on data landing page

[jenniferthibault]

What we're after: In order to ensure consistency across the data section, we should make sure that the featured cards on the data landing page reflect the most interesting and useful categories in the Advanced data section.

(Part of work to implement changes to new Advanced data section that integrates the data catalog and bulk data to the site)

Designs

Completion criteria

• Design new icon for Historical statistics (design task)
• Possibly redesign the icon for "Download bulk data" to incorporate a download action (design task)
• Export icons as .svg files, and add to this issue
• Re-order the cards so that the "Loans and debts" card is before the "Candidates" and "Committees" cards
• Add a card for historical statistics following "Filings and reports"
• Modify the bulk data card text from Bulk data and other sources to Download bulk data. Place this card last on the list
• Link Bulk data card to the link determined in this issue: https://github.com/18F/fec-cms/issues/1411

The "External sources" tab will still exist on Advanced data, but it's not a priority set of data, so it makes sense to remove it from this featured space. We'll be making the same changes to the menu (link to come)