Add some design time readable metadata to weld-*.jars for tooling

Working on JBIDE-8017 it became obvious that it would be good if Weld (and other spec implementations) jars could say which services they implement (and optionally how) so tooling could validate and navigate based on the classpath.

Opening this issue to not forget - suggested approach was to see if one could use the seam-beans.xml format (but under a different name, i.e. design-time-beans.xml) to help guide tooling.

This is to include not only spec required services but also additonal ones as for example http://docs.jboss.org/weld/reference/1.1.0.CR1/en-US/html/contexts.html#d0e5515