Dispatch Screen (Responder) #220

Create dispatch screen for responding organizations

• only accessible from responder accounts
• create dispatch directory in screens folder
• shows list of unclaimed issues within responder's selected service areas and selected categories
• clicking on issue navigates to issue detail screen
• list is sortable by date, endorsements, and proximity (can maybe work off of leaderboard screen)
• appropriate icon on navbar - possible a hamburger menu/list icon