feat(engine-rest): add deletion of identity links of tasks

related to CAM-1201
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
fix(ejb-client): mark ejb-client as distributable in web-fragment.xml

related to CAM-1292
fix(history): add NPE guards for startTime

related to CAM-1297
Merge branch 'master' of github.com:camunda/camunda-bpm-platform