Convert logging to logback predominantly via slf4j

This PR converts the underlying logging to logback throughout much of the codebase using the slf4j facade. use of jcl and jul by third-party libraries is handled by bridges. The import/insight stacks still use log4j but that will be dealt with in a separate branch. Thee are still small traces of log4j that need tidying up but again that can be done separately once this base work is merged in.

There is no easy way to test this other than the build being successful, the server running and functioning normally. All java logs should be present. slf4j configuration information should appear in master.out (this can be turned down once the work is complete).