Upgrade Wagon to use Java5 compatible libraries and finally drop old dependencies

I created a wagon-1.x branch for being able to maintain maven-2.0.x features (even if its unlikely that this will ever happen).

Wagon-2.x is requiring java >= 5 and thus we can (should!) drop old dependencies (e.g. avalon framework deps) and upgrade to the latest and greatest versions.

See WAGON-329 for an initial patch (starting point only).