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
fixed equality test bug in NodeFactory

there was a `=== null' check which does not cover cases of undefined
variables --> changed to `== null'
moved method definition out of the Class.create method

The TypeMapper.getInstance method did not work properly if defined
inside the Class.create method. I thus defined getInstance explicitly on
the TypeMapper function.
fixed equality test bug in TypeMapper

there was a `=== null' check which does not cover cases of undefined
variables --> changed to `== null'
added some test cases for NodeFactory
Merge branch 'feature-sponate' into develop

Conflicts:
	lib/rdf/TypeMapper.js