Add support to send unformatted messages and parameters to sentry server via logback

Hi.

To improve the consolidation of errors on the sentry server this change allows the sending of unformatted messages and any associated parameters to the Sentry server. It uses the sentry data interface sentry.interfaces.Message (http://sentry.readthedocs.org/en/latest/developer/interfaces/index.html#provided-interfaces). 

Our sentry server is now successfully grouping the same error messages even if their parameter values differ.

Cheers
Oliver