push: allow pushing new topic to non-publishing server by default This improves and fix the behavior change introduced by the new "topicmap". * Topics are properly ignored when pushing to a publishing server, * pushing new topics is allowed without --force a non-publishing server, * Pushing extra heads on a topic requires --force. Create of new head on a branch by phase movement is not properly detected for now. We'll improve that part in a later changesets. There is more awful monkey patching going on. We'll have to refactor core to get rid of them.