Fix intrinsic precision and accessibility specs

Just a fix for the two tests which began to fail with the last 10
commits.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Do not based snapshot identifier on its date

Apparently it was a mistake to base the snapshot identifier solely on
the date. At least through Mongoid I always receive non-identical
snapshots. Using a MongoDB generated identifier fixes this mess.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Revert batch import to single import

The batch import seems to be erroneous on some datasets. I do not get
any errors. With single import it works, for now I will use this slower
version until I can pinpoint the problem.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Use generated CKAN JSON schema

The CKAN schema that was used so far has been replaced with one that has
been generated from the CKAN schema itself. It adds a lot more fields
and makes the whole metric more accurate. It needs still adjustments,
but now the weighted completeness becomes more significant.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Activate CKAN instances on v1.7

Just a small sync, since the harvester supports now CKAN instances on
version 1.7.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>