Segregated support of unique index and unique constraint. Added missing commits: 400d73c8a1e4f53459a877c8652811ee22c0913b, e91811cb3fe3101d7d8ac95c45f8bc1ba9bd913a, a4ecf053186b11bc31fbff79ef36248500383908, d7d1c397a35735383b34632d3a67bbc3a3371a45, c71b3ae0425e5c039b047825dbf8351a773e6785, 2f9da39ec645b54d08c95649c99d7b87a32bdc72 and 9aa4e79aab0477b4212b01d65de53193d9559e39