refactor(operations): rename delete operation

- rename DeleteParticipantOperation
- add integration roundtrip test case to ensure functionality of the
  delete feature
fix(field injection util): use correct feature

Related CAM-1506
test(integration): add getFeatureProvider() method to Behavior

CAM-1496
fix(subprocess): Improve subprocess behavior

A collapsed subprocess has non-visible child elements
and an expanded subprocess has visible child elements.

An expanded subprocess has always the correct size to
show all child elements.

Add test cases to check this  improvement.

Delete Pullup and Pushdown feature from context menu.

related to #CAM-1500
test(callactivity/namespace): add test case for callActivity

- testcase to check namespace of call activity attributes

related to #CAM-1510
chore(project/dependencies): automatically include via maven

Instead of including dependencies in git repository, they are now
automatically included via maven-dependency-plugin.

BREAKING CHANGE:

You must execute `mvn clean install` on the project to copy the latest
modeler dependencies to the lib directories.
docs(contributing): Add hint on dependency unpack
docs(custom-task): add images