Use helpers to govern the alter table statements
Fix bug where we weren't issing the ADD in front of foreign keys
If we're making a table static, truncate before we make any changes to it
Move all index/constraint changes to after other table changes, including static data
If we're dropping a table, don't try to add/remove constraints from it
Stop trying to emit PRIMARY KEY and UNIQUE as field attributes

This interferes with deferring constraint creation.
Resume disabling foreign key checks until such time as we add PREPARE WITH syntax to constraints
Stop adding extraneous commas, add_index is part of a list now and that means that's handled for us
Merge pull request #294 from iarna/misc

Changes to improve ordering of constraints to avoid foreign key issues