Modify Trie to make it sparse and lazily initialized as far as possible.

Add longestMatch(), shortestMatch() and partialSearch() methods for different kinds of Trie lookup.

Expand test coverage for Tries

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1439943 13f79535-47bb-0310-9956-ffa450edef68