rake: move the package tasks to lib/killbill

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
rake: rework Rake tasks

Make the directory structure inside the tarball Killbill-friendly, i.e.
one should just have to untar the plugin inside the bundles/ruby directory for
Killbill to auto-detect it.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
killbill.rb: don't fail to load killbill if Java APIs can't be found

There are usecases (e.g. irb debugging) when we want to be able to load
the Ruby APIs, even though the Java ones are not available.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
rake: reduce verbosity in Rake tasks

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
Merge branch 'master' of github.com:killbill/killbill-plugin-framework-ruby