Merge pull request #26 from obiba/feature/MICA-933-100k-variables

Multiple fixes: MICA-944, MICA-934, MICA-967
Fix block anchors
Change DCE population cardinality
Change DCE population cardinality
Use CNR for study/population noderef
Upgrading Bootstrap theme to 2.0-beta3
MICA-933: Creating variables using a batch operation
MICA-933: Deleting nodes with entity_delete_multiple instead of deleting each nodes separately