Some minor tweak to non-UX VoltTable and tweaks to VoltTable schema tests

1. Move the VoltTable metadata that is used for test code into a single class with a single final instance variable. Clean up some other stuff to make that work well.
1. Generate ALTER TABLE when given two slightly different VoltTables with metadata.
1. Add partitioning support to VoltTables with metadata and add partitioning support to the shorthand for making tables.
1. A bit of additional schema changing test code for ALTER TABLE and for partitioned tables.
1. Test schema changes with fake data or with empty tables.
1. Other minor tweaks.