Disallow previously deprecated usage of track properties in meta block

[danielmitterdorfer]

In #183, which we released with Rally 0.4.7, we deprecated usage of description, short-description and data-url in the track meta-block and we should remove this deprecation layer now.

This was valid (but deprecated) before:

{
  "meta": {
    "short-description": "60.8M POIs from PlanetOSM",
    "description": "This test indexes 60.8M documents (POIs from PlanetOSM, total 2.3 GB json) using 8 client threads and 5000 docs per bulk request against Elasticsearch",
    "data-url": "http://benchmarks.elasticsearch.org.s3.amazonaws.com/corpora/geopoint"
  }
}

Now, the only supported syntax is:

{
  "short-description": "60.8M POIs from PlanetOSM",
  "description": "This test indexes 60.8M documents (POIs from PlanetOSM, total 2.3 GB json) using 8 client threads and 5000 docs per bulk request against Elasticsearch",
  "data-url": "http://benchmarks.elasticsearch.org.s3.amazonaws.com/corpora/geopoint",
}