code: public boolean isVersionable( Name primaryType,
                                    Collection<Name> mixinTypes ) {
          if (primaryType != null && versionableNodeTypeNames.contains(primaryType)) return true;
          for (Name mixinType : mixinTypes) {
              if (versionableNodeTypeNames.contains(mixinType)) return true;
          }
          return false;
      }
docs: Determine if at least one of the named primary node type or mixin types is or subtypes the 'mix:versionable' mixin type.
  
  @param primaryType the primary type name; may be null
  @param mixinTypes the mixin type names; may not be null but may be empty
  @return true if any of the named node types is versionable, or false if there are none