Trello clone

[InesaFitsner]

Part 1 scope:

• [x] in-memory store service for application data with ability to replace with data base for future versions
• [x] drag and drop for cards between lists within one board
• [x] separate URL routes to boards and main app pages (screens)
• [x] multiple files: all data entities and user controls are in separate files
• [x] follow Python code style
• [x] consistent UI across the app:
  • [ ] dialog buttons
  • [x] Trello-like list design
  • [ ] standard color theme
  • [x] horizontal scrolling for board lists
  • [x] vertical scrolling for cards in a list

Out of scope:

• Search
• Theming
• Profile
• Multiple users/authentication
• Database
• Toggle