minor changes

- added Error constructor in a throw statetemen
- removed comma after the last entry in a dictionary/hash map
added first tests

- 100% test coverage for rdf/anon-id-str.js
- 100% test coverage for rdf/anon-id.js
- 100% test coverage for rdf/base-datatype.js
- 100% test coverage for rdf/literal-label.js
Merge branch 'develop' of https://github.com/GeoKnow/Jassa-Core into develop
fixed require paths in tests
renamed existing test files

...in accordance with the names of the files that are tested