added doap.rdf for projects.apache.org use

@andywenk per your ["CouchDB not listet (sic) at apache.org" thread](http://www.mail-archive.com/dev@couchdb.apache.org/msg30050.html).

In theory, providing that to the ASF should be all that's needed:
http://projects.apache.org/guidelines.html

Additionally, someone should let the ASF know that their DOAP generator is down. :frowning: 
Submission of form at http://projects.apache.org/create.html
Returns 500 on http://projects.apache.org/make_doap.cgi