Move Talkilla SPA specific files into their own directory

Part of the work for [this card](https://trello.com/c/zDjIeyL3).

This reorganises the Talkilla SPA files into a new /spa/talkilla/ directory, with appropriate sub-directories for js and img.

This is the first step in the card for allowing to configure with different SPAs. Future cards will allow selection of the directory based on configuration values, and allow for more configuration details.

This PR also manages updating the SPA record in the database, as otherwise the user would be stuck trying to load an old SPA record. Rather than deleting the SPA record, I chose to update it if a new SPA record comes in - deleting the SPA record feels fragile in the case of a network issue. If the user logged in again, and the details had been updated, then the SPA record would be updated appropriately.