Minor: clean-up/refactoring
Fix #680 "Exception with simple xxf:control="true""

- filter properties/last-id
Fix #675 "Repeat: missing rowspan messes up table"

- statically determine set of extension attributes for each control
- clarify handling of style attribute
- style attribute is never output in Ajax response so update schema
- output extension attributes in no namespace (except class) in Ajax response
- small clean-up, renaming and refactoring