move transaction code to its own file
implement with-logical-transaction, ensure-transaction, commit-hooks, and abort-hooks
Allow more than one form in the body of pomo:ensure-transaction.

Also refactored so that the macro expands into a function
call (call-with-ensured-transaction) so that there's a function that can
be traced (and that appears on the call stack) and so that there's less
back quoting.
Revert "Evaluate the arguments passed in via the s-sql:$$ placeholder with cl-postgres:to-sql-string"

This reverts commit 80f42e94be3c0192eeefdd270df0f57d2fe27fe2.
Fix asd dependency, remove-trailing-whitespace