echonest: Turn off song identification

[sampsyo]

The EN API is turning off fingerprint and upload-based song identification. In other words, Echoprint is dead, and it also looks like the upload-to-analyze API will no longer include an ID for fetching the bulk of the metadata.

So we should probably remove these parts of the Echo Nest plugin:

• Fingerprinting
• Uploading
• Transcoding for upload
• Truncation for upload

which leaves matching by MBID and conventional metadata (artist/title).

Probably not a bad idea to start exploring an AcousticBrainz plugin as a replacement…

[sampsyo]

Just removed fingerprinting. I'm leaving in the upload-based analysis—it's not clear from the announcement how well that will continue to work, but it seems like we may still be able to get acoustic metrics from audio data.