Expose cardinality checker via the cli

[glguy]

See #986

[saratge]

I am getting the error shown below after ingesting using this ingestion package: gsn_demo.zip

The error appears to arise from python semtk client

[weisenje]

Checking cardinality against the package that @saratge is loading generates this SPARQL, which errors. @cuddihyge and @weisenje will investigate further.

SELECT DISTINCT ?subject (COUNT(?object) AS ?object_COUNT)  
    FROM <[http://rack001/data>](http://rack001/data%3E)
WHERE { 
  ?subject a ?subject_class .   VALUES ?subject_class { b0  } .
OPTIONAL { ?subject <[http://sadl.org/GSN-Pattern-core.sadl#isPat>](http://sadl.org/GSN-Pattern-core.sadl#isPat%3E) ?object } . 
} GROUP BY ?subject 
  HAVING ( ?object_COUNT != 1 )

[cuddihyge]

The cardinality bug has to do with @saratge 's use of unions inside SADL statements, which are correct, but no one had used before with SemTK.
I can fix it on the master branch.
This bug has nothing to do with @glguy 's work on this branch.
I'm fine merging this branch.
The bug will persist until I make another semtk release and add it to RACK.

[cuddihyge]

I opened #989 to address the bug.

[weisenje]

Thanks @glguy. Remember to document this on the Wiki when you get a chance.