Merge pull request #147 from tmciver-basis/master

Changes in support of AUT-714 and AUT-725
Promoted 'getUniquePath' method from AbstractFile to Content interface.
Refactored implementation of 'getUniquePath' in several implementing
classes. These changes in support of AUT-753.
Merge branch 'master' of https://github.com/sleuthkit/sleuthkit