Implement WithConnection for sqlserver database driver

[selaux]

Similar methods have already been implemented for the mysql and postgres database. This adds WithConnection(ctx context.Context, conn *sql.Conn, config *Config) (*SQLServer, error) to the SQL Server database driver as well.

Issues/PRs for this can be found here:

• Issue: Database driver closes the connection pool #578
• PR for MySQL: Added a method to create a mysql database from a connection object #583
• PR for Postgresql: Add WithConnection to Postgres similar to MySQL. #659

I tried to align as close as possible to the other implementations.

Note: The linter errors dont seem to be related to the contents of this PR.

[coveralls]

Coverage increased (+0.03%) to 57.804% when pulling a5148ef on selaux:implement-with-connection-for-sql-server into 03613f1 on golang-migrate:master.