Add support for Microsoft SQL Server

I spent a few hours getting CommaFeed to work with Microsoft SQL Server. I used the JTDS JDBC driver, LGPL-licensed. Most of the time was spent learning all the technologies used so I could understand where to make the proper changes! The only annoying problem was figuring out that Liquibase was failing when it was trying to upgrade the schema and tracking where that was set. The changelog used the CEIL function, which in SQL Server is named CEILING.