* multiple business data have a persistenceId_string contract input (on
task) in order to provide an edition behavior by default. Associated
operation script has been updated. Operator is now "takes value of"
* Idem for multiple reference in aggregation/composition
* For aggregation, the contract input is now persistenceId_string
instead of persistenceId, in order to avoid potential issues related to
js behavior (Long max range isn't the same ...)

closes [BST-101](https://bonitasoft.atlassian.net/browse/BST-101)