timob-12176: fix a bunch of issues

Fixes include: 
-showVerticalIndicator should work properly when toggle on/off
-correct sectionIndex, itemIndex values
-events won't bubble past listItem (iOS parity)
-allow defaultItemTemplate to change
-implement updateItemAt. This behaves same as replaceItemsAt. This implementation is for parity with iOS.
-replaceItemsAt no longer append when trying to replace an item with index = items.size()
-'items' is now a property in section, with read/write capabilities.
-fix layout glitches for built-in template
-'wordWrap' property in label is now true by default.