Introduced ResultSet::Auditlog

Hi.

I introduced DBIx::Class::ResultSet::Auditlog, which addresses the problem that occured
when 'delete' or 'update' is called on a resultset by delegating to 'delete_all' and 'update_all'.

I included some tests which work on DBIC::Relationship, and which failed before using teh AuditLog rs-class.

Additionally, i modified the 'Action' table and the main auditlog module to support tables with more than one primary key.

I did not include extra test for that, but it is tested inside my relationship-tests (the bookauthor table has two pks, thats how i found out that two pks are not supported at the moment).

I am not sure if all my updates are realy 'good'. In fact, it is a hotfix which i use in one of my applications. Review is definetly required. 

I hope it is not offending, but i added a 'contributors' section to the readme, and added my name.
If you don't want to include my patches, feel free to remove it. But If you include my patches, or parts of it, I would be very glad to see my name in the docs :)

For hints and questions: email me, or contact me via irc (lukast).

Cheers, Lukas