Display errors / statuses to user

[agrieser]

Sometimes the spotify api returns errors (especially when searching). We need some way to display / indicate that an error has occurred in the UI. I think we could use something similar to what interchange does.

[agrieser]

Api errors are now handled on the server side, and are sent back to the user. Now we need to display them.

[tonywok]

Added a way to display errors to the user. Let me know what you think or how it can be improved.

Reopen if you don't like the fix.

[agrieser]

I simplified the interface for creating the messages, and moved those methods to the Spotbox namespace.

[tonywok]

thumbs up.