OPENNLP-674 Use tokenizer from the factory

git-svn-id: https://svn.apache.org/repos/asf/opennlp/trunk@1587956 13f79535-47bb-0310-9956-ffa450edef68
OPENNLP-673 Added prefix to the NGram feature generator

git-svn-id: https://svn.apache.org/repos/asf/opennlp/trunk@1587969 13f79535-47bb-0310-9956-ffa450edef68