Implement new commission meetings index page

[noahmanger]

So that users can more easily find commission meetings, remove them from the "latest updates" feed and create a new page for "Commission meetings".

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This is still being designed.

Completion criteria:

• Implement the page as designed
• Move all meetings/hearings pages from Latest updates feed to meetings feed (https://www.fec.gov/updates/ --> https://www.fec.gov/meetings/)
• Remove "commission meetings" from latest updates "publication type" dropdown
• Account for all redirect rules / link issues https://github.com/18F/fec-proxy/issues/59

[jenniferthibault]

🎨 Styled interactive prototype in InVision
(the side nav is interactive)

Design notes:

• Each category should default to showing all years, with the ability to narrow down by year
• Should support searching by keyword (like current latest updates does)
• Question: @noahmanger do you think we should we add filter validation like in the data tables to show that results have changed/search term applied?
• Hearings should show the full title, since they have more variance, but open meetings adn executive summaries should be titled with just the date
• Ability to mark a meeting a cancelled
• Feed uses the simple table pattern (hey! look! the pattern library in action!)

Content need:

• Intro copy to Hearings section (cc @jameshupp )

[jenniferthibault]

@johnnyporkchops just wanted to check in on this—i see it's in "Done" but the completion criteria aren't finished. Can you give an update?