improvements on UI stability: added 'data-' prefix to attributes; span around editable areas only in body (again); diverse fixes and enhancements
Merge branch 'feature/ui_rework' of github.com:structr/structr into feature/ui_rework

Conflicts:
	structr-ui/src/main/java/org/structr/web/entity/dom/DOMElement.java
Merge branch 'feature/ui_rework' of github.com:structr/structr into feature/ui_rework