feat(formFields): Added new tab "Form Fields" to configure form data for
user task and start event.

- it is possible to set id, label, type, defaultValue, properties,
  validation constraints and value to a form field
- implement new change filter for mapping tables to match changes in a
complex business object
- extends ecore model for form fields
- rename "NestedFeatureChangeFilter" to "IsManyAttributeAnyChildChangeFilter"

- "Form Fields" tab is deactivated until camunda engine release doesn't
  support this feature

related to #CAM-1398