fix api calls
handle null values
unit test dataset deleter
fix entity explorer, support mref values
Merge pull request #679 from dennishendriksen/master

Fix entity explorer, support mref values
Merge pull request #680 from bartcharbon/master

Unit Test for the dataset delete function
Merge branch 'master' of https://github.com/molgenis/molgenis
Added data item list
Added unittests