Added JSON test filed from ProvToolbox and unification tests
All the ProvToolbox's JSON was generated by the version https://github.com/trungdong/ProvToolbox/commit/bf13da78a5cdc409571fc9cbe9454597e4dd31fc with the dictionary-related files removed.
Unification test cases are taken from https://dvcs.w3.org/hg/prov/raw-file/default/testcases/process.html (only 9 at the moment)

Note: These are the files missing in #47