Multiple iterations of the local track mig tool

Experimenting with multiple implementations of the utility I am writing
to migrate local tracks to spotify tracks
- - using spotify api search in desktop client is fast but errors out
when you give it too many tracks (>500)
- - Now using spotify metadata service and just passe an array of local
track uris, to the server, which parses each url and uses that info to
search for the tracks. Constraining the search to just tracks seems to
have imporved the speed tremendously

Finished refactoring spapp.js