raco: fix bug #240

In the rule RemoveUnusedColumns, I added code to change the
grouping_list and aggregate_list attributes of algebra.GroupBy. There
was a third member variable, column_list, that was defined redundantly
to be grouping_list + aggregate_list.... however, I did not update that
field as well. After the bugfixes of this morning in #229, that
column_list variable was read for the first and only time and thus a bug
was triggered.

Fix this by simply removing that attribute and replacing it with a
function that returns grouping_list + aggregate_list and thus always
keeps the invariant true.
raco: add test for bug #240

also remove stray print statements in the tests.
Merge pull request #241 from uwescience/fix-240

Fix 240
Standalone example program
Add load to myrial grammer
Add file scan operator to algebra
fakedb implementation of load
Add dump command and operator
Add Dump to fakedb
Add standalone option to myrial script
Add get_types method to scheme
Fix production rule for load
sample datasets
Fix type conversion in fakedb
Fix department schema
Fix typo in input data
algebra: make DoWhile its own operator

Not a subclass of Sequence, it's a different thing.
myrial.interpreter: pass the physical plan instead of the plan tuple

fixes issues with fraudulent parallels getting appended to the top
myrialang: compile DoWhile

Includes minor refactoring to the serialization of relation key
enable json for pagerank and sigmaclipping

Also fix the evaluation semantics of DoWhile