Journal Statistics Framework and Dryad Utils API

This changeset includes 

1. A framework for calculating per-journal statistics, and command-line tool (org.datadryad.journalstatistics)
2. Classes providing Dryad-specifc operations for Data Packages and Data Files (org.datadryad.api)
3. Improved support for automated tests (A base test class, a testing database)

Notes on running tests locally:

See [Dryad Wiki: Testing](http://wiki.datadryad.org/Testing#Test_Configuration) for detailed instructions on configuring tests. You should be able to bring up a [vagrant-dryad](https://github.com/datadryad/vagrant-dryad) VM and run `test_dryad.sh`. Also, this branch has been tested by [Travis CI](https://travis-ci.org/dleehr/dryad-repo/builds/29994148) from the [dleehr fork](https://github.com/dleehr/dryad-repo).

Running the tests requires a dspace directory, e.g.

    mvn package -DskipTests=false -Ddefault.dspace.dir=/opt/dryad/test

This directory must contain a config directory, with a dspace.cfg and a default.license file. The tests will use the configuration (including database credentials) specified  dspace.cfg file.  You can find a sample dryad-test directory in dryad-repo/test.