- fixed a couple of variable rowheight examples where we do not bluntly replace/overwrite the DataView.getIemMetaData() function but provide a (custom) metadata provider instead.

- removed obsoleted example 15 and renumbered examples 16a+16b to 15+16
- groupItemMetadataProvider options: treat the totals row just like the group row: have options for both 'selectable' and 'focusable' for each

- completed default option set with getRowMetadata=null for documentation's sake (no effect on execution)