ref #8107 getFieldGroup() returns Optional to avoid NPEs and logging errors before rethrowing as PopupEditorException
fix #7588 updating buttons on setDataSource
ref #7361 creating new icon 'create-new' & introducing ButtonFactory for harmonization of button creation
fix #7246 consitent implementation of LazySelect reloading of modified entity beans:
fix #6999 generic button state updater for toOne relation field
ref #6169 first implementation of delete operations
ref #6169 implementing lazy loading ToOneRelatedEntityCombobox field and using it for inReferences
ref #6169 RelatedEntityListSelect (ToOneRelatedEntityField) edit and select working, add blocked by #6673