Added missing "discourse" grammatical relation type.

Hi Rupert,

In this pull request I just added a missing grammatical relation type - discourse. This request should be merged after the latest patch from https://issues.apache.org/jira/browse/STANBOL-1132 is committed in trunk (see my latest comment in the jira).

I don't know how to start a discussion on github so I'm putting this here as well:
Also I ran the new junit tests after your refactoring with the parser annotator in the pipeline and it crashed with an OutOfMemoryException. I saw that you included several more documents with larger text in the tests and the I suppose the issue is that the parser annotator can't handle it (I had MAVEN_OPTS=-Xmx2048M).Maybe at this moment there should be a limit to the length of the text that can be processed when the parser annotator is activated?

Also related to the way the build is done, I ran for the first time mvn clean install from the root folder and it gave me errors about models/seg/ files missing so I had to call models/download_models.sh first. From your description on the main page I understand that the english server should not have any dependencies on the international server models?