PostgreSQL Auto Increment/DEFAULT values fix

##### Added right brace to view of default value in Auto Increment columns.
Actually this:
`integer Auto Increment [nextval('sequence_name']`
is changed to:
`integer Auto Increment [nextval('sequence_name')]`.

##### Added option to set `nextval('sequence_name')` as DEFAULT value on column.

When you adding DEFAULT value to column and that value is `nextval('sequence_name')`, you'll get an error, because of wrong quoting. Value is now compared against `^ DEFAULT \'\s*nextval\\(\'\'(.*)\'\'\\)\s*\'$` and if match, alter command will look like `... SET DEFAULT nextval('sequence_name') ...`.