Do not use anymore shaded version of wagon-http as it we can control commons-logging version

Integrated the fix toward 1.521.

Integrated the new version of remoting

The plan of the record is that we start producing 1.6 class files and
see if people start complaining. If we hear from users, we'll re-visit
our decision, and if we don't, then we'll start using 1.6 features
everywhere in the code.