Create new top-level SVN space for shared Maven-ish code

The upshot of this issue is that we have an opportunity to consolidate APIs used by many plugins and other tools tangential to Maven itself. These supporting projects should have release cycles largely independent of Maven, so we don' t have to wait for a new release of Maven to take advantage of new features/bugfixes in these libraries.

Think Jakarta commons, only for Maven.

I've asked for a vote to setup a new top-level SVN space for such projects, alongside components/ and plugins/. Following the template used for the mojo project at codehaus, this space will entail a single trunk/branches/tags structure.