[INTERNAL] P13nColumnsPanel: remove condenser

- additional API docu
- condenser for columnsItems was removed
- no columnsItems will be removed any more
- always the maximum of changes will be reflected in columnsItems
- smaller bug fixes

Change-Id: I86d146352d864e2a434f66bcef32b56b411319ae
Merge "[INTERNAL] P13nColumnsPanel: remove condenser"