fix(subprocess): Add handling for collapsed and expanded subprocess.

- DI for a new subprocess has attribute "isExpanded=true", for that it is
  necessary to override the method "createDi"
- default value of attribute "isExpanded" is "false"
- change handling of "BPMNDIAttributeDefault.USE_DI_VALUE" to get the
  DI value of the current BPMNShape for subprocesses
- change super class of "ExpandFlowNodeFeature" because it seems that the
  old super class "ShowDiagramPageFeature" make no sense in the subprocess
  context

related to #CAM-1500
fix(formFields): Fix NPE in form field mapping table and improve usability in details dialog.

- add OK button deactivation when value of id and type field was deleted
- add new test case for the deletion of user task extension value
  and fix with this one the NPE in form field mapping table -> add
  one more notification change filter

related to #CAM-1398
fix(di/defaults): apply defaults on di create only

DI defaults are used and applied when the DI is newly created, only.

Simplifies subprocess#isExpanded detection.

Related to CAM-1500
feat(formFields/dialog): squash changes on OK

Partial implementation of git versioning system ships with this commit.

- upon OK press in dialog, changes are squashed (áka minified) to a
single re- and undoable command
- functionality is available in CommandUtil

Related to CAM-1398
fix(call-activity): make call activities unresizable