refactored the CommonDataStructure class -> moved to main src folder and
created static methods (the goal of this class is to have some "global"
variables which can be shared within all metrics, thus metrics using it
should not have the "new" initaliser). Fixed the Dereferencibility class
- now also checking the predicate triple for dereferencibilty (as the
predicate is a URI as well). Please not that with these changes, the
UnstructuredData Class will not work.
Merge branch 'master' of https://github.com/diachron/quality.git

Conflicts:
	src/main/java/de/unibonn/iai/eis/diachron/qualitymetrics/utilities/CommonDataStructures.java