Dashboard: Filter & sort hackathons on list view

[garyhtou]

Filter by:

• Approved
• Rejected
• Pending (requested by @devramsean0)

Sort by:

• Start date
• Created at (submission date)

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Nice to have:

• Filter by "Upcoming" (start date in the future; today and onwards)
  e.g. where("start >= ?", Time.now)