chore(engine): make iomapping parsing reusable by connect plugin

- also adds a BpmnParseException which can be used in process
  engine plugins to add Errors to the parser

related to #CAM-2706
chore(engine): add scope key to variable scope

related to #CAM-2706
chore(engine): allow service task parse listener to add behavior

related to #CAM-2706
chore(engine): remove connect from engine

related to #CAM-2706
chore(qa): remove connect integration test

related to #CAM-2706
chore(pom): use connect SNAPSHOT until next release also use BOM

related to #CAM-2741
chore(pom): add connect dependency to distro and standalone webapps

- also add connect plugin to process engine configuration of distro
  and standalone webapps

related to #CAM-2706