Exercise compile to JSON for myrial test programs
Map countall to a count of column zero
Skip JSON compilation for sigma-clipping tests
Skip JSON compilation of reachable test
Skip JSON testing for unsupported operators
Skip JSON testing for pagerank tests
Skip JSON tests for kmeans
Fix some flake errors
Change intersect, difference operators to have set semantics
Add a unique ID to sigma clipping schema
Change set difference tests to have set semantics
Fix intersection to have set semantics
Merge pull request #155 from uwescience/andrew_compile_to_json

Exercise JSON compilation in MyriaL tests