Add URI routing and history (back / forward) with confirmation

[AlanSl]

Implements the most difficult part of https://trello.com/c/yc5v94HL/108-general-navigation

• [x] Back and forward buttons work with selecting data and widgets
• [x] URL reflects current data and widget
• [x] Confirmation dialog is shown before data is unloaded
• [x] Logo points to home page and also uses confirmation dialog before unloading data
• [x] Data samples and widgets can be selected from URL
• [x] Reloading a page with a websocket or file upload URL opens the appropriate data selector