[WIP] Test table api

Unfinished. Commit to get a review on changes I made to the Table constructor. For some reason types were not automatically being inferred from the call to discover(data) regardless of the kind of data. I could probably simplify this more by modifying the conditionals above the statement that I added. Relatively simply fix. 
If selxpr is only used in this one test then lets just define it here.  Keeping everything in one place will help people who need to read this test later.