Add regression testing to confirm consistency of clinical table schemas with column_metadata

[fedorov]

Follow up on #35

A (relatively!) easy regression test should be, for each table_name in column_metadata, take the list of variable_name, and confirm that the list of columns from the schema in the corresponding table is exactly that. We should have a regression check and run this test on every update of the clinical metadata tables. I will submit a follow up separate ticket on that.

[G-White-ISB]

I have updated the code generating clinical tables to check for consistency between the column_metadata table and the actual columns in the table when the tables are generated. It will report inconsistencies through stdout message. It noticed the problem with the hnscc_3dct_rt_clinical table.

[fedorov]

Great! Can you add a pointer to that piece of code here, for the sake of completeness, and for my information?