added support for "csv" serializable

This is a "quick and dirty CSV" storage engine, but there is a really good "use case" for this engine

http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_find-in-set

with `FIND_IN_SET()` you can look in fields with CSV values for a single key/string i
without having to do any awkward LIKE wildcarding, etc.
Merge pull request #97 from zeroasterisk/develop

added support for "csv" serializable