Fix quoting of unique_together constraint and table names.
Review Request #9882 — Created April 30, 2018 and submitted
When generating SQL statements for managing unique_together constraints,
the table names and constraint names weren't being quoted, which was
causing a problem on a particular Postgres database. This was
inconsistent with other SQL statements.
All table names and constraint names are now quoted and all test SQL
statements have been audited to check for other quoting issues.
Unit tests pass.
SQL verified by a user who hit this problem.