Add ability to produce a count of objects in the database (by :pace class)

[mgrbyte]

During a wormbase ACeDB release, a "count of objects per class" report is generated.

In order to give us confidence that the data is the right ballpark post import, add the ability to generate the same style of output/report.

• Add a "canned" datalog query that uses the :pace metadata to retrieve a count of each class.
• Wrap this in a command line script that outputs to standard out and/or a file

[mgrbyte]

Use the same command as detailed in #7 as the "entry-point" for this implementation of this feature.

[mgrbyte]

Fixed by #18