MusicBrainz Server should move away from using Perl as the server code.

To do this, we decided at Summit 2013 that these things need to be done:

1. Pick a simple entity - for example, Series or URLs.
2. Implement ws/3 for this entity, and implement any required minimal ws/3 functionality for related entities.
3. Create a data aggregation service to create JSON blobs from different ws/3 responses.
4. Create a minimal Perl front-end which queries the aggregation service once for each template to be rendered.
5. Repeat for other entities, one at a time.
6. Remove the all minimal Perl front-ends and replace them with something else.

Discussed at http://chatlogs.musicbrainz.org/musicbrainz-devel/2013/2013-09/2013-09-30.html#T19-15-12-920285