Initial copy of DataPackage and D1Object classes from DataONEorg/rdataone package.

These classes are direct copies of the classes from the `rdataone` package, specifically from commit 681b5bbdc7facac133476c19855c5ed6220c2c1c.  They depend on rJava, which needs to be removed before this is useful.  This commit records the starting point before refactoring of the class to remove he java dependency was started.
Initial test infrastructure for DataPackage class.

Refactoring just getting under way to remove java and dataone dependencies. Closes #6.