rework www plugin pkg creation (again)

With previous version, the plugins shared "static" directory inside site-package dir!

We create one real module dir per plugin, so that we can use pkg_resource to store
the built js.

This way, we even have bdist_egg working and are ready for py2exe :)

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Waterfall with guanlecoja-ui