add build listener support to output

replace system.out's and system.err's and other logging with a sort of build listener like Ant uses (perhaps reusing their classes?)

I'm not sure to what extent this happens throughout parts other than maven-core which could make it difficult - but I think as long as maven core and the ant listener are configured to a new one, then it is feasible.

This facilitates capturing build output for purposes such as archiving nightly builds or emailing failures.

IS this worth doing on maven-current, or is it likely to change significantly for maven-new?