SMAP: Implement minimal routing and async loading

[linzjax]

Part of the Map Single Page App epic (#1031)

Task

• The URL displayed in the address bar is in sync with the current view.
• The view is updated according to the URL when users access the page via a permalink.
  • (Possibly of help: A JavaScript router in 20 lines)
• Implement async loading into the client-side.
  • Design and implement a framework to handle information flows uni directional.
  • Changes to the UI only happen when the URL in the browser changes.
  • URL in the browser changes and triggers an event, which will load the resource from the backend and display some loading info to the user.
  • Upon receiving the response, the loading info is removed, and the contents are displayed in the panel.
  • Track the app's current state in one central variable and update only the state when the user interacts with the platform.
  • Add listeners that track changes to the state and update the UI according to the current state.

[linzjax]

Follow-up Tasks

• Update Search to work with hash changing.

[oliverroick]

Let's be honest; we'll never dig this up from the graveyard of unfinished work. Closing.