add aggregatable attributes
Fix xref/mref indexing, some refactoring
Merge pull request #1816 from Mark-de-Haan/master

Fix typo. Javascript solution to prevent readonly attributes to be edited
Merge branch 'master' of https://github.com/molgenis/molgenis into feature/indexingrepo
Merge pull request #1818 from dennishendriksen/feature/indexingrepo

Fix xref/mref indexing, meta data handling refactoring