dont use repr to quote string in compare_server_default

dont use repr to quote string in compare_server_default

Fixed issue where server default compare would not work for string defaults
that contained backslashes, due to mis-rendering of these values when
comparing their contents.

The server default comparison still has a lot of not-robust behaviors,
however at least get in place a parameterized test suite so that we
can add new scenarios quickly.

Made a slight adjustment to SQLite's compare server default implementation
to better handle defaults with or without parens around them, from both
the reflected and the local metadata side.

Implemented basic server default comparison for the Oracle backend;
previously, Oracle's formatting of reflected defaults prevented any
matches from occurring.

Change-Id: If5a69eec4b22d243a564d2c89e78ae33ba5be88f
Fixes: #1145