Data Index processing events in groups

[fjtirado]

Description

apache/incubator-kie-issues#1457 allows the possibility of grouping event publishing.
Data index and data audit were modified to be able to consume the new events, but they are still processed individually.
While this is perfectly fine for data audit, in the case of data index it will be pretty interesting, from performance point of view, to be able to process them in groups, achieving a potentially huge performance gain

Implementation ideas

Modify indexing and storage interfaces to accept collection of ProcessInstaceDataEvent and UserTaskInstanceEvent
This way, in the JPA implementation we can take full benefit of the hibernate optimitazion when several sets are invoked within the same transaciton.