New odlparent Maven Profile / Parent / whatever-it-takes to be able to build a JavaDoc site

based on discussions rovarga, zxiiro and I just had on IRC:

current limitations of https://nexus.opendaylight.org/content/sites/site/ "include but are not limited to" :

• nexus hosted JavaDoc is not Google web search engine spider indexed

• too many clicks to go from root to JavaDoc of 1 class; mvn site more distracting and not helpful in this context

• linking between classes of artefacts within projects and cross projects broken (e.g. https://nexus.opendaylight.org/content/sites/site/org.opendaylight.yangtools/carbon/yang-model-util/apidocs/org/opendaylight/yangtools/yang/model/util/AbstractSchemaContext.html)

as the first step to get real JavaDoc for ODL, we'd need a new odlparent Maven Profile / Parent / whatever-it-takes to be able to build a JavaDoc site for a given project, across all artefacts of a project.