updated maven-publish-ext so that excluded dependencies are excluded in ...

...published maven pom

@Deravel please review.  Take a look at the changes to MavenPublishExtExtension; the level of nesting makes me throw up in my mouth a bit but I don't have a better solution b/c it's writing xml and I don't think it makes sense to break up into separate methods but take a look and let me know.

FYI, this will only fix maven-publish-ext, not maven-ext.  Which means, it will fix bancvue-internal and everything downstream but will not fix gradle-core.  So, we'll still need to exclude guava in bancvue-internal but nothing downstream, which is probably good enough.