Update DOAP file and publish

DOAP file exists, https://github.com/apache/incubator-zeppelin/blob/gh-pages/doap.rdf

but not updated (remove incubating tag) and not published by specifying it's location at https://svn.apache.org/repos/asf/comdev/projects.apache.org/data/projects.xml.

More informations can be found https://projects.apache.org/create.html

Once it's done, information will be available in https://projects.apache.org/project.html?zeppelin